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	$80.49	9.364%	$88.0271	$88.03	$88.05	$88.00
Purchase #2	$13.58	5.676%	$14.3508	$14.35	$14.35	$14.40
Purchase #3	$124.34	3.362%	$128.5203	$128.52	$128.50	$128.50
Purchase #4	$131.97	12.578%	$148.5692	$148.57	$148.55	$148.60
Purchase #5	$172.59	11.701%	$192.7848	$192.78	$192.80	$192.80
Purchase #6	$247.83	10.341%	$273.4581	$273.46	$273.45	$273.50
Purchase #7	$88.83	7.783%	$95.7436	$95.74	$95.75	$95.70
7 purchase totals =	$859.63		$941.4539	$941.45	$941.45	$941.50