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	$129.25	9.676%	$141.7562	$141.76	$141.75	$141.80
Purchase #2	$66.72	8.613%	$72.4666	$72.47	$72.45	$72.50
Purchase #3	$108.68	10.708%	$120.3175	$120.32	$120.30	$120.30
Purchase #4	$213.48	10.331%	$235.5346	$235.53	$235.55	$235.50
Purchase #5	$146.75	10.781%	$162.5711	$162.57	$162.55	$162.60
Purchase #6	$193.84	5.666%	$204.823	$204.82	$204.80	$204.80
Purchase #7	$205.54	8.240%	$222.4765	$222.48	$222.50	$222.50
7 purchase totals =	$1,064.26		$1,159.9455	$1,159.95	$1,159.90	$1,160.00