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	$215.80	6.475%	$229.7731	$229.77	$229.75	$229.80
Purchase #2	$201.42	10.314%	$222.1945	$222.19	$222.20	$222.20
Purchase #3	$186.86	5.132%	$196.4497	$196.45	$196.45	$196.40
Purchase #4	$105.46	5.621%	$111.3879	$111.39	$111.40	$111.40
Purchase #5	$72.90	10.653%	$80.666	$80.67	$80.65	$80.70
Purchase #6	$136.95	6.650%	$146.0572	$146.06	$146.05	$146.10
Purchase #7	$192.86	13.180%	$218.2789	$218.28	$218.30	$218.30
7 purchase totals =	$1,112.25		$1,204.8073	$1,204.81	$1,204.80	$1,204.90