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	$62.74	3.307%	$64.8148	$64.81	$64.80	$64.80
Purchase #2	$106.45	3.487%	$110.1619	$110.16	$110.15	$110.20
Purchase #3	$65.25	12.366%	$73.3188	$73.32	$73.30	$73.30
Purchase #4	$35.33	13.529%	$40.1098	$40.11	$40.10	$40.10
Purchase #5	$72.53	12.556%	$81.6369	$81.64	$81.65	$81.60
Purchase #6	$51.91	13.738%	$59.0414	$59.04	$59.05	$59.00
Purchase #7	$111.46	7.596%	$119.9265	$119.93	$119.95	$119.90
7 purchase totals =	$505.67		$549.0101	$549.01	$549.00	$548.90