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	$86.95	3.517%	$90.008	$90.01	$90.00	$90.00
Purchase #2	$75.85	3.287%	$78.3432	$78.34	$78.35	$78.30
Purchase #3	$36.71	5.386%	$38.6872	$38.69	$38.70	$38.70
Purchase #4	$84.90	7.556%	$91.315	$91.32	$91.30	$91.30
Purchase #5	$183.58	11.338%	$204.3943	$204.39	$204.40	$204.40
Purchase #6	$93.31	7.623%	$100.423	$100.42	$100.40	$100.40
Purchase #7	$143.44	7.309%	$153.924	$153.92	$153.90	$153.90
7 purchase totals =	$704.74		$757.0947	$757.09	$757.05	$757.00