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	$218.83	11.188%	$243.3127	$243.31	$243.30	$243.30
Purchase #2	$212.88	3.454%	$220.2329	$220.23	$220.25	$220.20
Purchase #3	$48.69	11.741%	$54.4067	$54.41	$54.40	$54.40
Purchase #4	$170.90	8.314%	$185.1086	$185.11	$185.10	$185.10
Purchase #5	$48.83	5.395%	$51.4644	$51.46	$51.45	$51.50
Purchase #6	$170.70	6.511%	$181.8143	$181.81	$181.80	$181.80
Purchase #7	$138.87	5.488%	$146.4912	$146.49	$146.50	$146.50
7 purchase totals =	$1,009.70		$1,082.8308	$1,082.82	$1,082.80	$1,082.80