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	$121.97	5.198%	$128.31	$128.31	$128.30	$128.30
Purchase #2	$55.84	7.274%	$59.9018	$59.90	$59.90	$59.90
Purchase #3	$26.30	8.216%	$28.4608	$28.46	$28.45	$28.50
Purchase #4	$89.93	10.871%	$99.7063	$99.71	$99.70	$99.70
Purchase #5	$52.45	4.602%	$54.8637	$54.86	$54.85	$54.90
Purchase #6	$151.44	11.309%	$168.5663	$168.57	$168.55	$168.60
Purchase #7	$222.70	4.377%	$232.4476	$232.45	$232.45	$232.40
7 purchase totals =	$720.63		$772.2565	$772.26	$772.20	$772.30