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	$73.54	4.487%	$76.8397	$76.84	$76.85	$76.80
Purchase #2	$82.67	8.171%	$89.425	$89.43	$89.45	$89.40
Purchase #3	$229.87	4.829%	$240.9704	$240.97	$240.95	$241.00
Purchase #4	$64.52	13.255%	$73.0721	$73.07	$73.05	$73.10
Purchase #5	$247.75	6.753%	$264.4806	$264.48	$264.50	$264.50
Purchase #6	$130.44	13.269%	$147.7481	$147.75	$147.75	$147.70
Purchase #7	$212.82	4.321%	$222.016	$222.02	$222.00	$222.00
7 purchase totals =	$1,041.61		$1,114.5519	$1,114.56	$1,114.55	$1,114.50