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	$93.80	10.248%	$103.4126	$103.41	$103.40	$103.40
Purchase #2	$134.83	9.688%	$147.8923	$147.89	$147.90	$147.90
Purchase #3	$48.48	11.638%	$54.1221	$54.12	$54.10	$54.10
Purchase #4	$96.76	7.621%	$104.1341	$104.13	$104.15	$104.10
Purchase #5	$115.50	13.182%	$130.7252	$130.73	$130.75	$130.70
Purchase #6	$245.90	3.529%	$254.5778	$254.58	$254.60	$254.60
Purchase #7	$6.55	13.829%	$7.4558	$7.46	$7.45	$7.50
7 purchase totals =	$741.82		$802.3199	$802.32	$802.35	$802.30