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	$184.39	6.450%	$196.2832	$196.28	$196.30	$196.30
Purchase #2	$156.59	7.399%	$168.1761	$168.18	$168.20	$168.20
Purchase #3	$57.31	11.389%	$63.837	$63.84	$63.85	$63.80
Purchase #4	$238.93	7.442%	$256.7112	$256.71	$256.70	$256.70
Purchase #5	$77.40	4.741%	$81.0695	$81.07	$81.05	$81.10
Purchase #6	$59.61	4.272%	$62.1565	$62.16	$62.15	$62.20
Purchase #7	$103.35	9.846%	$113.5258	$113.53	$113.55	$113.50
7 purchase totals =	$877.58		$941.7593	$941.77	$941.80	$941.80