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	$103.28	4.502%	$107.9297	$107.93	$107.95	$107.90
Purchase #2	$136.39	13.654%	$155.0127	$155.01	$155.00	$155.00
Purchase #3	$66.56	7.660%	$71.6585	$71.66	$71.65	$71.70
Purchase #4	$232.82	4.726%	$243.8231	$243.82	$243.80	$243.80
Purchase #5	$184.43	3.846%	$191.5232	$191.52	$191.50	$191.50
Purchase #6	$147.84	3.647%	$153.2317	$153.23	$153.25	$153.20
Purchase #7	$70.72	7.621%	$76.1096	$76.11	$76.10	$76.10
7 purchase totals =	$942.04		$999.2885	$999.28	$999.25	$999.20