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	$151.97	7.543%	$163.4331	$163.43	$163.45	$163.40
Purchase #2	$130.89	3.690%	$135.7198	$135.72	$135.70	$135.70
Purchase #3	$20.67	3.731%	$21.4412	$21.44	$21.45	$21.40
Purchase #4	$81.91	10.596%	$90.5892	$90.59	$90.60	$90.60
Purchase #5	$205.37	8.711%	$223.2598	$223.26	$223.25	$223.30
Purchase #6	$162.35	10.476%	$179.3578	$179.36	$179.35	$179.40
Purchase #7	$189.91	8.217%	$205.5149	$205.51	$205.50	$205.50
7 purchase totals =	$943.07		$1,019.3158	$1,019.31	$1,019.30	$1,019.30