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	$100.45	10.400%	$110.8968	$110.90	$110.90	$110.90
Purchase #2	$181.39	13.286%	$205.4895	$205.49	$205.50	$205.50
Purchase #3	$140.97	5.626%	$148.901	$148.90	$148.90	$148.90
Purchase #4	$173.59	9.717%	$190.4577	$190.46	$190.45	$190.50
Purchase #5	$114.26	12.225%	$128.2283	$128.23	$128.25	$128.20
Purchase #6	$118.33	12.109%	$132.6586	$132.66	$132.65	$132.70
Purchase #7	$134.44	11.726%	$150.2044	$150.20	$150.20	$150.20
7 purchase totals =	$963.43		$1,066.8363	$1,066.84	$1,066.85	$1,066.90