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	$14.32	3.415%	$14.809	$14.81	$14.80	$14.80
Purchase #2	$59.96	13.324%	$67.9491	$67.95	$67.95	$67.90
Purchase #3	$83.86	6.676%	$89.4585	$89.46	$89.45	$89.50
Purchase #4	$32.56	3.323%	$33.642	$33.64	$33.65	$33.60
Purchase #5	$144.64	10.206%	$159.402	$159.40	$159.40	$159.40
Purchase #6	$12.95	10.618%	$14.325	$14.33	$14.35	$14.30
Purchase #7	$208.54	12.399%	$234.3969	$234.40	$234.40	$234.40
7 purchase totals =	$556.83		$613.9825	$613.99	$614.00	$613.90