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	$144.69	4.858%	$151.719	$151.72	$151.70	$151.70
Purchase #2	$134.58	8.361%	$145.8322	$145.83	$145.85	$145.80
Purchase #3	$53.39	6.557%	$56.8908	$56.89	$56.90	$56.90
Purchase #4	$152.27	6.303%	$161.8676	$161.87	$161.85	$161.90
Purchase #5	$46.86	9.476%	$51.3005	$51.30	$51.30	$51.30
Purchase #6	$57.82	11.229%	$64.3126	$64.31	$64.30	$64.30
Purchase #7	$226.36	7.439%	$243.1989	$243.20	$243.20	$243.20
7 purchase totals =	$815.97		$875.1216	$875.12	$875.10	$875.10