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	$250.31	9.692%	$274.57	$274.57	$274.55	$274.60
Purchase #2	$44.85	7.640%	$48.2765	$48.28	$48.30	$48.30
Purchase #3	$159.53	5.858%	$168.8753	$168.88	$168.90	$168.90
Purchase #4	$118.25	7.442%	$127.0502	$127.05	$127.05	$127.10
Purchase #5	$87.48	3.112%	$90.2024	$90.20	$90.20	$90.20
Purchase #6	$153.81	7.314%	$165.0597	$165.06	$165.05	$165.10
Purchase #7	$230.90	8.251%	$249.9516	$249.95	$249.95	$250.00
7 purchase totals =	$1,045.13		$1,123.9857	$1,123.99	$1,124.00	$1,124.20