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	$149.59	10.538%	$165.3538	$165.35	$165.35	$165.40
Purchase #2	$21.31	4.756%	$22.3235	$22.32	$22.30	$22.30
Purchase #3	$6.73	11.757%	$7.5212	$7.52	$7.50	$7.50
Purchase #4	$38.36	12.793%	$43.2674	$43.27	$43.25	$43.30
Purchase #5	$134.82	11.148%	$149.8497	$149.85	$149.85	$149.80
Purchase #6	$242.58	13.231%	$274.6758	$274.68	$274.70	$274.70
Purchase #7	$159.47	7.268%	$171.0603	$171.06	$171.05	$171.10
7 purchase totals =	$752.86		$834.0517	$834.05	$834.00	$834.10