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	$103.88	7.522%	$111.6939	$111.69	$111.70	$111.70
Purchase #2	$202.41	7.700%	$217.9956	$218.00	$218.00	$218.00
Purchase #3	$26.43	5.274%	$27.8239	$27.82	$27.80	$27.80
Purchase #4	$78.61	6.680%	$83.8611	$83.86	$83.85	$83.90
Purchase #5	$53.54	8.233%	$57.9479	$57.95	$57.95	$57.90
Purchase #6	$145.62	13.438%	$165.1884	$165.19	$165.20	$165.20
Purchase #7	$61.86	8.790%	$67.2975	$67.30	$67.30	$67.30
7 purchase totals =	$672.35		$731.8083	$731.81	$731.80	$731.80