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	$91.29	9.391%	$99.863	$99.86	$99.85	$99.90
Purchase #2	$208.34	4.113%	$216.909	$216.91	$216.90	$216.90
Purchase #3	$79.74	13.530%	$90.5288	$90.53	$90.55	$90.50
Purchase #4	$30.52	7.423%	$32.7855	$32.79	$32.80	$32.80
Purchase #5	$246.39	10.579%	$272.4556	$272.46	$272.45	$272.50
Purchase #6	$158.92	9.646%	$174.2494	$174.25	$174.25	$174.20
Purchase #7	$185.91	7.634%	$200.1024	$200.10	$200.10	$200.10
7 purchase totals =	$1,001.11		$1,086.8937	$1,086.90	$1,086.90	$1,086.90