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	$170.94	8.773%	$185.9366	$185.94	$185.95	$185.90
Purchase #2	$113.73	8.263%	$123.1275	$123.13	$123.15	$123.10
Purchase #3	$169.66	11.655%	$189.4339	$189.43	$189.45	$189.40
Purchase #4	$178.89	11.858%	$200.1028	$200.10	$200.10	$200.10
Purchase #5	$108.59	3.327%	$112.2028	$112.20	$112.20	$112.20
Purchase #6	$207.58	5.565%	$219.1318	$219.13	$219.15	$219.10
Purchase #7	$54.68	5.486%	$57.6797	$57.68	$57.70	$57.70
7 purchase totals =	$1,004.07		$1,087.6151	$1,087.61	$1,087.70	$1,087.50