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	$110.46	11.571%	$123.2413	$123.24	$123.25	$123.20
Purchase #2	$45.50	13.184%	$51.4987	$51.50	$51.50	$51.50
Purchase #3	$6.27	3.231%	$6.4726	$6.47	$6.45	$6.50
Purchase #4	$145.58	6.610%	$155.2028	$155.20	$155.20	$155.20
Purchase #5	$41.82	7.437%	$44.9302	$44.93	$44.95	$44.90
Purchase #6	$58.84	12.428%	$66.1526	$66.15	$66.15	$66.20
Purchase #7	$41.76	8.556%	$45.333	$45.33	$45.35	$45.30
7 purchase totals =	$450.23		$492.8312	$492.82	$492.85	$492.80