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	$99.48	12.470%	$111.8852	$111.89	$111.90	$111.90
Purchase #2	$118.46	11.391%	$131.9538	$131.95	$131.95	$132.00
Purchase #3	$208.45	7.807%	$224.7237	$224.72	$224.70	$224.70
Purchase #4	$243.57	9.695%	$267.1841	$267.18	$267.20	$267.20
Purchase #5	$139.32	10.852%	$154.439	$154.44	$154.45	$154.40
Purchase #6	$98.86	4.512%	$103.3206	$103.32	$103.30	$103.30
Purchase #7	$93.89	7.371%	$100.8106	$100.81	$100.80	$100.80
7 purchase totals =	$1,002.03		$1,094.3170	$1,094.31	$1,094.30	$1,094.30