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	$199.52	12.251%	$223.9632	$223.96	$223.95	$224.00
Purchase #2	$21.74	12.552%	$24.4688	$24.47	$24.45	$24.50
Purchase #3	$223.84	6.723%	$238.8888	$238.89	$238.90	$238.90
Purchase #4	$230.54	3.251%	$238.0349	$238.03	$238.05	$238.00
Purchase #5	$109.80	9.472%	$120.2003	$120.20	$120.20	$120.20
Purchase #6	$97.44	9.184%	$106.3889	$106.39	$106.40	$106.40
Purchase #7	$61.79	9.164%	$67.4524	$67.45	$67.45	$67.50
7 purchase totals =	$944.67		$1,019.3973	$1,019.39	$1,019.40	$1,019.50