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	$160.76	8.117%	$173.8089	$173.81	$173.80	$173.80
Purchase #2	$60.78	9.262%	$66.4094	$66.41	$66.40	$66.40
Purchase #3	$185.41	3.105%	$191.167	$191.17	$191.15	$191.20
Purchase #4	$121.66	5.816%	$128.7357	$128.74	$128.75	$128.70
Purchase #5	$66.72	8.123%	$72.1397	$72.14	$72.15	$72.10
Purchase #6	$166.43	10.625%	$184.1132	$184.11	$184.10	$184.10
Purchase #7	$181.53	3.123%	$187.1992	$187.20	$187.20	$187.20
7 purchase totals =	$943.29		$1,003.5731	$1,003.58	$1,003.55	$1,003.50