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	$94.40	13.214%	$106.874	$106.87	$106.85	$106.90
Purchase #2	$48.32	10.231%	$53.2636	$53.26	$53.25	$53.30
Purchase #3	$175.74	7.613%	$189.1191	$189.12	$189.10	$189.10
Purchase #4	$189.85	10.709%	$210.181	$210.18	$210.20	$210.20
Purchase #5	$52.46	13.842%	$59.7215	$59.72	$59.70	$59.70
Purchase #6	$34.49	8.209%	$37.3213	$37.32	$37.30	$37.30
Purchase #7	$54.76	12.864%	$61.8043	$61.80	$61.80	$61.80
7 purchase totals =	$650.02		$718.2848	$718.27	$718.20	$718.30