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	$73.89	4.638%	$77.317	$77.32	$77.30	$77.30
Purchase #2	$210.48	6.191%	$223.5108	$223.51	$223.50	$223.50
Purchase #3	$146.58	11.299%	$163.1421	$163.14	$163.15	$163.10
Purchase #4	$228.30	4.521%	$238.6214	$238.62	$238.60	$238.60
Purchase #5	$99.92	11.369%	$111.2799	$111.28	$111.30	$111.30
Purchase #6	$222.80	4.112%	$231.9615	$231.96	$231.95	$232.00
Purchase #7	$48.58	3.627%	$50.342	$50.34	$50.35	$50.30
7 purchase totals =	$1,030.55		$1,096.1747	$1,096.17	$1,096.15	$1,096.10