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	$88.64	4.167%	$92.3336	$92.33	$92.35	$92.30
Purchase #2	$200.43	10.774%	$222.0243	$222.02	$222.00	$222.00
Purchase #3	$232.64	11.385%	$259.1261	$259.13	$259.15	$259.10
Purchase #4	$74.65	10.427%	$82.4338	$82.43	$82.45	$82.40
Purchase #5	$147.78	11.805%	$165.2254	$165.23	$165.25	$165.20
Purchase #6	$136.60	10.567%	$151.0345	$151.03	$151.05	$151.00
Purchase #7	$154.75	4.187%	$161.2294	$161.23	$161.25	$161.20
7 purchase totals =	$1,035.49		$1,133.4071	$1,133.40	$1,133.50	$1,133.20