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	$221.70	10.582%	$245.1603	$245.16	$245.15	$245.20
Purchase #2	$238.45	12.852%	$269.0956	$269.10	$269.10	$269.10
Purchase #3	$78.73	12.406%	$88.4972	$88.50	$88.50	$88.50
Purchase #4	$34.69	13.419%	$39.3451	$39.35	$39.35	$39.30
Purchase #5	$39.71	13.580%	$45.1026	$45.10	$45.10	$45.10
Purchase #6	$242.64	6.240%	$257.7807	$257.78	$257.80	$257.80
Purchase #7	$67.47	13.264%	$76.4192	$76.42	$76.40	$76.40
7 purchase totals =	$923.39		$1,021.4007	$1,021.41	$1,021.40	$1,021.40