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	$239.68	4.160%	$249.6507	$249.65	$249.65	$249.70
Purchase #2	$156.89	6.654%	$167.3295	$167.33	$167.35	$167.30
Purchase #3	$133.32	3.123%	$137.4836	$137.48	$137.50	$137.50
Purchase #4	$46.76	13.266%	$52.9632	$52.96	$52.95	$53.00
Purchase #5	$44.70	12.631%	$50.3461	$50.35	$50.35	$50.30
Purchase #6	$60.90	11.542%	$67.9291	$67.93	$67.95	$67.90
Purchase #7	$214.57	3.748%	$222.6121	$222.61	$222.60	$222.60
7 purchase totals =	$896.82		$948.3143	$948.31	$948.35	$948.30