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	$145.77	12.739%	$164.3396	$164.34	$164.35	$164.30
Purchase #2	$7.48	4.730%	$7.8338	$7.83	$7.85	$7.80
Purchase #3	$175.67	9.258%	$191.9335	$191.93	$191.95	$191.90
Purchase #4	$49.69	12.413%	$55.858	$55.86	$55.85	$55.90
Purchase #5	$79.45	3.843%	$82.5033	$82.50	$82.50	$82.50
Purchase #6	$242.57	8.282%	$262.6596	$262.66	$262.65	$262.70
Purchase #7	$50.38	7.743%	$54.2809	$54.28	$54.30	$54.30
7 purchase totals =	$751.01		$819.4087	$819.40	$819.45	$819.40