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	$98.33	13.311%	$111.4187	$111.42	$111.40	$111.40
Purchase #2	$72.84	7.792%	$78.5157	$78.52	$78.50	$78.50
Purchase #3	$12.56	4.375%	$13.1095	$13.11	$13.10	$13.10
Purchase #4	$98.88	4.836%	$103.6618	$103.66	$103.65	$103.70
Purchase #5	$6.95	4.720%	$7.278	$7.28	$7.30	$7.30
Purchase #6	$93.54	13.360%	$106.0369	$106.04	$106.05	$106.00
Purchase #7	$34.34	5.462%	$36.2157	$36.22	$36.20	$36.20
7 purchase totals =	$417.44		$456.2363	$456.25	$456.20	$456.20