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	$48.73	9.351%	$53.2867	$53.29	$53.30	$53.30
Purchase #2	$61.32	9.592%	$67.2018	$67.20	$67.20	$67.20
Purchase #3	$242.65	13.243%	$274.7841	$274.78	$274.80	$274.80
Purchase #4	$11.26	8.507%	$12.2179	$12.22	$12.20	$12.20
Purchase #5	$143.66	8.144%	$155.3597	$155.36	$155.35	$155.40
Purchase #6	$72.96	7.245%	$78.246	$78.25	$78.25	$78.20
Purchase #7	$37.48	8.556%	$40.6868	$40.69	$40.70	$40.70
7 purchase totals =	$618.06		$681.7830	$681.79	$681.80	$681.80