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	$121.43	3.588%	$125.7869	$125.79	$125.80	$125.80
Purchase #2	$151.66	10.191%	$167.1157	$167.12	$167.10	$167.10
Purchase #3	$228.49	11.239%	$254.17	$254.17	$254.15	$254.20
Purchase #4	$85.49	4.255%	$89.1276	$89.13	$89.15	$89.10
Purchase #5	$247.70	7.816%	$267.0602	$267.06	$267.05	$267.10
Purchase #6	$223.30	3.551%	$231.2294	$231.23	$231.25	$231.20
Purchase #7	$99.48	6.328%	$105.7751	$105.78	$105.80	$105.80
7 purchase totals =	$1,157.55		$1,240.2649	$1,240.28	$1,240.30	$1,240.30