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	$142.88	11.220%	$158.9111	$158.91	$158.90	$158.90
Purchase #2	$71.43	10.301%	$78.788	$78.79	$78.80	$78.80
Purchase #3	$191.50	5.731%	$202.4749	$202.47	$202.45	$202.50
Purchase #4	$33.84	11.766%	$37.8216	$37.82	$37.80	$37.80
Purchase #5	$141.82	7.476%	$152.4225	$152.42	$152.40	$152.40
Purchase #6	$97.69	4.870%	$102.4475	$102.45	$102.45	$102.40
Purchase #7	$237.70	7.226%	$254.8762	$254.88	$254.90	$254.90
7 purchase totals =	$916.86		$987.7418	$987.74	$987.70	$987.70