Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$216.25	10.187%	$238.2794	$238.28	$238.30	$238.30
Purchase #2	$102.65	8.874%	$111.7592	$111.76	$111.75	$111.80
Purchase #3	$244.71	10.394%	$270.1452	$270.15	$270.15	$270.10
Purchase #4	$150.64	11.242%	$167.5749	$167.57	$167.55	$167.60
Purchase #5	$250.76	7.403%	$269.3238	$269.32	$269.30	$269.30
Purchase #6	$175.67	11.278%	$195.4821	$195.48	$195.50	$195.50
Purchase #7	$183.88	8.683%	$199.8463	$199.85	$199.85	$199.80
7 purchase totals =	$1,324.56		$1,452.4109	$1,452.41	$1,452.40	$1,452.40