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	$185.46	6.171%	$196.9047	$196.90	$196.90	$196.90
Purchase #2	$12.64	11.210%	$14.0569	$14.06	$14.05	$14.10
Purchase #3	$24.43	3.285%	$25.2325	$25.23	$25.25	$25.20
Purchase #4	$45.35	7.120%	$48.5789	$48.58	$48.60	$48.60
Purchase #5	$10.35	7.251%	$11.1005	$11.10	$11.10	$11.10
Purchase #6	$133.66	5.474%	$140.9765	$140.98	$141.00	$141.00
Purchase #7	$89.76	7.657%	$96.6329	$96.63	$96.65	$96.60
7 purchase totals =	$501.65		$533.4829	$533.48	$533.55	$533.50