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	$119.84	3.179%	$123.6497	$123.65	$123.65	$123.60
Purchase #2	$123.82	6.495%	$131.8621	$131.86	$131.85	$131.90
Purchase #3	$29.73	3.270%	$30.7022	$30.70	$30.70	$30.70
Purchase #4	$232.95	4.538%	$243.5213	$243.52	$243.50	$243.50
Purchase #5	$28.84	12.145%	$32.3426	$32.34	$32.35	$32.30
Purchase #6	$190.55	13.103%	$215.5178	$215.52	$215.50	$215.50
Purchase #7	$69.74	9.717%	$76.5166	$76.52	$76.50	$76.50
7 purchase totals =	$795.47		$854.1123	$854.11	$854.05	$854.00