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	$53.52	13.498%	$60.7441	$60.74	$60.75	$60.70
Purchase #2	$44.89	3.176%	$46.3157	$46.32	$46.30	$46.30
Purchase #3	$141.53	4.330%	$147.6582	$147.66	$147.65	$147.70
Purchase #4	$62.57	8.228%	$67.7183	$67.72	$67.70	$67.70
Purchase #5	$57.91	13.145%	$65.5223	$65.52	$65.50	$65.50
Purchase #6	$250.48	5.806%	$265.0229	$265.02	$265.00	$265.00
Purchase #7	$153.49	11.646%	$171.3654	$171.37	$171.35	$171.40
7 purchase totals =	$764.39		$824.3469	$824.35	$824.25	$824.30