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	$229.74	9.315%	$251.1403	$251.14	$251.15	$251.10
Purchase #2	$5.60	9.393%	$6.126	$6.13	$6.15	$6.10
Purchase #3	$173.25	8.799%	$188.4943	$188.49	$188.50	$188.50
Purchase #4	$135.68	11.701%	$151.5559	$151.56	$151.55	$151.60
Purchase #5	$92.42	13.226%	$104.6435	$104.64	$104.65	$104.60
Purchase #6	$162.45	11.333%	$180.8605	$180.86	$180.85	$180.90
Purchase #7	$190.58	3.296%	$196.8615	$196.86	$196.85	$196.90
7 purchase totals =	$989.72		$1,079.6820	$1,079.68	$1,079.70	$1,079.70