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	$102.74	8.654%	$111.6311	$111.63	$111.65	$111.60
Purchase #2	$211.72	5.350%	$223.047	$223.05	$223.05	$223.00
Purchase #3	$51.67	3.440%	$53.4474	$53.45	$53.45	$53.40
Purchase #4	$244.52	7.618%	$263.1475	$263.15	$263.15	$263.10
Purchase #5	$228.26	6.335%	$242.7203	$242.72	$242.70	$242.70
Purchase #6	$7.55	5.278%	$7.9485	$7.95	$7.95	$7.90
Purchase #7	$112.32	8.561%	$121.9357	$121.94	$121.95	$121.90
7 purchase totals =	$958.78		$1,023.8775	$1,023.89	$1,023.90	$1,023.60