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	$30.94	7.411%	$33.233	$33.23	$33.25	$33.20
Purchase #2	$136.69	13.614%	$155.299	$155.30	$155.30	$155.30
Purchase #3	$184.45	8.828%	$200.7332	$200.73	$200.75	$200.70
Purchase #4	$180.57	12.597%	$203.3164	$203.32	$203.30	$203.30
Purchase #5	$105.28	6.563%	$112.1895	$112.19	$112.20	$112.20
Purchase #6	$226.29	10.794%	$250.7157	$250.72	$250.70	$250.70
Purchase #7	$128.28	6.369%	$136.4502	$136.45	$136.45	$136.50
7 purchase totals =	$992.50		$1,091.9370	$1,091.94	$1,091.95	$1,091.90