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	$186.81	9.300%	$204.1833	$204.18	$204.20	$204.20
Purchase #2	$103.28	3.525%	$106.9206	$106.92	$106.90	$106.90
Purchase #3	$54.64	11.380%	$60.858	$60.86	$60.85	$60.90
Purchase #4	$151.85	13.702%	$172.6565	$172.66	$172.65	$172.70
Purchase #5	$196.96	7.190%	$211.1214	$211.12	$211.10	$211.10
Purchase #6	$99.49	4.786%	$104.2516	$104.25	$104.25	$104.30
Purchase #7	$133.83	12.634%	$150.7381	$150.74	$150.75	$150.70
7 purchase totals =	$926.86		$1,010.7295	$1,010.73	$1,010.70	$1,010.80