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	$243.64	12.612%	$274.3679	$274.37	$274.35	$274.40
Purchase #2	$198.92	6.301%	$211.4539	$211.45	$211.45	$211.50
Purchase #3	$85.62	6.566%	$91.2418	$91.24	$91.25	$91.20
Purchase #4	$156.72	11.540%	$174.8055	$174.81	$174.80	$174.80
Purchase #5	$87.55	3.110%	$90.2728	$90.27	$90.25	$90.30
Purchase #6	$87.95	3.314%	$90.8647	$90.86	$90.85	$90.90
Purchase #7	$244.61	13.195%	$276.8863	$276.89	$276.90	$276.90
7 purchase totals =	$1,105.01		$1,209.8929	$1,209.89	$1,209.85	$1,210.00