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	$57.25	6.596%	$61.0262	$61.03	$61.05	$61.00
Purchase #2	$198.41	11.268%	$220.7668	$220.77	$220.75	$220.80
Purchase #3	$185.33	3.375%	$191.5849	$191.58	$191.60	$191.60
Purchase #4	$200.33	5.849%	$212.0473	$212.05	$212.05	$212.00
Purchase #5	$151.74	12.249%	$170.3266	$170.33	$170.35	$170.30
Purchase #6	$127.60	11.217%	$141.9129	$141.91	$141.90	$141.90
Purchase #7	$91.77	8.248%	$99.3392	$99.34	$99.35	$99.30
7 purchase totals =	$1,012.43		$1,097.0039	$1,097.01	$1,097.05	$1,096.90