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	$190.79	12.454%	$214.551	$214.55	$214.55	$214.60
Purchase #2	$221.86	3.467%	$229.5519	$229.55	$229.55	$229.60
Purchase #3	$53.83	9.869%	$59.1425	$59.14	$59.15	$59.10
Purchase #4	$80.33	7.625%	$86.4552	$86.46	$86.45	$86.50
Purchase #5	$36.94	7.729%	$39.7951	$39.80	$39.80	$39.80
Purchase #6	$157.81	10.797%	$174.8487	$174.85	$174.85	$174.80
Purchase #7	$204.58	10.587%	$226.2389	$226.24	$226.25	$226.20
7 purchase totals =	$946.14		$1,030.5833	$1,030.59	$1,030.60	$1,030.60