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	$209.33	4.685%	$219.1371	$219.14	$219.15	$219.10
Purchase #2	$168.88	12.201%	$189.485	$189.49	$189.50	$189.50
Purchase #3	$195.92	13.673%	$222.7081	$222.71	$222.70	$222.70
Purchase #4	$57.54	6.211%	$61.1138	$61.11	$61.10	$61.10
Purchase #5	$137.54	4.222%	$143.3469	$143.35	$143.35	$143.30
Purchase #6	$174.36	12.587%	$196.3067	$196.31	$196.30	$196.30
Purchase #7	$225.90	10.821%	$250.3446	$250.34	$250.35	$250.30
7 purchase totals =	$1,169.47		$1,282.4422	$1,282.45	$1,282.45	$1,282.30