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	$224.73	13.539%	$255.1562	$255.16	$255.15	$255.20
Purchase #2	$233.85	6.673%	$249.4548	$249.45	$249.45	$249.50
Purchase #3	$195.55	10.652%	$216.38	$216.38	$216.40	$216.40
Purchase #4	$81.66	9.691%	$89.5737	$89.57	$89.55	$89.60
Purchase #5	$26.95	6.470%	$28.6937	$28.69	$28.70	$28.70
Purchase #6	$87.47	5.265%	$92.0753	$92.08	$92.10	$92.10
Purchase #7	$89.56	3.143%	$92.3749	$92.37	$92.35	$92.40
7 purchase totals =	$939.77		$1,023.7086	$1,023.70	$1,023.70	$1,023.90