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	$53.37	8.565%	$57.9411	$57.94	$57.95	$57.90
Purchase #2	$58.54	3.109%	$60.36	$60.36	$60.35	$60.40
Purchase #3	$85.35	6.345%	$90.7655	$90.77	$90.75	$90.80
Purchase #4	$161.80	4.535%	$169.1376	$169.14	$169.15	$169.10
Purchase #5	$89.62	10.784%	$99.2846	$99.28	$99.30	$99.30
Purchase #6	$116.98	9.278%	$127.8334	$127.83	$127.85	$127.80
Purchase #7	$133.80	8.681%	$145.4152	$145.42	$145.40	$145.40
7 purchase totals =	$699.46		$750.7374	$750.74	$750.75	$750.70