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	$191.91	12.625%	$216.1386	$216.14	$216.15	$216.10
Purchase #2	$195.31	10.198%	$215.2277	$215.23	$215.25	$215.20
Purchase #3	$170.55	8.790%	$185.5413	$185.54	$185.55	$185.50
Purchase #4	$101.58	7.684%	$109.3854	$109.39	$109.40	$109.40
Purchase #5	$51.37	6.807%	$54.8668	$54.87	$54.85	$54.90
Purchase #6	$189.32	11.342%	$210.7927	$210.79	$210.80	$210.80
Purchase #7	$137.30	6.189%	$145.7975	$145.80	$145.80	$145.80
7 purchase totals =	$1,037.34		$1,137.7500	$1,137.76	$1,137.80	$1,137.70