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	$32.69	9.562%	$35.8158	$35.82	$35.80	$35.80
Purchase #2	$102.96	6.790%	$109.951	$109.95	$109.95	$110.00
Purchase #3	$172.96	4.291%	$180.3817	$180.38	$180.40	$180.40
Purchase #4	$110.77	11.160%	$123.1319	$123.13	$123.15	$123.10
Purchase #5	$170.43	8.484%	$184.8893	$184.89	$184.90	$184.90
Purchase #6	$179.88	10.869%	$199.4312	$199.43	$199.45	$199.40
Purchase #7	$55.96	12.104%	$62.7334	$62.73	$62.75	$62.70
7 purchase totals =	$825.65		$896.3343	$896.33	$896.40	$896.30