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	$150.96	3.715%	$156.5682	$156.57	$156.55	$156.60
Purchase #2	$238.85	6.589%	$254.5878	$254.59	$254.60	$254.60
Purchase #3	$105.44	5.402%	$111.1359	$111.14	$111.15	$111.10
Purchase #4	$183.87	4.294%	$191.7654	$191.77	$191.75	$191.80
Purchase #5	$219.64	12.451%	$246.9874	$246.99	$247.00	$247.00
Purchase #6	$101.41	11.172%	$112.7395	$112.74	$112.75	$112.70
Purchase #7	$61.88	12.460%	$69.5902	$69.59	$69.60	$69.60
7 purchase totals =	$1,062.05		$1,143.3744	$1,143.39	$1,143.40	$1,143.40