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	$137.45	9.171%	$150.0555	$150.06	$150.05	$150.10
Purchase #2	$145.67	12.549%	$163.9501	$163.95	$163.95	$164.00
Purchase #3	$11.32	7.433%	$12.1614	$12.16	$12.15	$12.20
Purchase #4	$98.57	7.251%	$105.7173	$105.72	$105.70	$105.70
Purchase #5	$100.59	4.497%	$105.1135	$105.11	$105.10	$105.10
Purchase #6	$148.95	10.333%	$164.341	$164.34	$164.35	$164.30
Purchase #7	$135.55	11.374%	$150.9675	$150.97	$150.95	$151.00
7 purchase totals =	$778.10		$852.3063	$852.31	$852.25	$852.40