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	$40.39	12.633%	$45.4925	$45.49	$45.50	$45.50
Purchase #2	$155.72	4.475%	$162.6885	$162.69	$162.70	$162.70
Purchase #3	$46.69	13.392%	$52.9427	$52.94	$52.95	$52.90
Purchase #4	$18.36	5.723%	$19.4107	$19.41	$19.40	$19.40
Purchase #5	$77.62	5.680%	$82.0288	$82.03	$82.05	$82.00
Purchase #6	$45.84	11.594%	$51.1547	$51.15	$51.15	$51.20
Purchase #7	$196.59	11.179%	$218.5668	$218.57	$218.55	$218.60
7 purchase totals =	$581.21		$632.2847	$632.28	$632.30	$632.30