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	$58.97	4.836%	$61.8218	$61.82	$61.80	$61.80
Purchase #2	$168.28	12.693%	$189.6398	$189.64	$189.65	$189.60
Purchase #3	$231.29	3.165%	$238.6103	$238.61	$238.60	$238.60
Purchase #4	$88.35	9.714%	$96.9323	$96.93	$96.95	$96.90
Purchase #5	$118.96	10.281%	$131.1903	$131.19	$131.20	$131.20
Purchase #6	$69.36	3.144%	$71.5407	$71.54	$71.55	$71.50
Purchase #7	$247.30	11.446%	$275.606	$275.61	$275.60	$275.60
7 purchase totals =	$982.51		$1,065.3412	$1,065.34	$1,065.35	$1,065.20