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	$103.82	6.615%	$110.6877	$110.69	$110.70	$110.70
Purchase #2	$168.35	10.405%	$185.8668	$185.87	$185.85	$185.90
Purchase #3	$80.58	12.500%	$90.6525	$90.65	$90.65	$90.70
Purchase #4	$146.68	12.573%	$165.1221	$165.12	$165.10	$165.10
Purchase #5	$6.69	4.142%	$6.9671	$6.97	$6.95	$7.00
Purchase #6	$173.45	10.781%	$192.1496	$192.15	$192.15	$192.10
Purchase #7	$32.63	13.559%	$37.0543	$37.05	$37.05	$37.10
7 purchase totals =	$712.20		$788.5001	$788.50	$788.45	$788.60