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	$133.37	11.743%	$149.0316	$149.03	$149.05	$149.00
Purchase #2	$84.33	13.287%	$95.5349	$95.53	$95.55	$95.50
Purchase #3	$238.25	10.459%	$263.1686	$263.17	$263.15	$263.20
Purchase #4	$69.97	12.825%	$78.9437	$78.94	$78.95	$78.90
Purchase #5	$181.69	7.522%	$195.3567	$195.36	$195.35	$195.40
Purchase #6	$99.47	5.791%	$105.2303	$105.23	$105.25	$105.20
Purchase #7	$118.73	11.137%	$131.953	$131.95	$131.95	$132.00
7 purchase totals =	$925.81		$1,019.2188	$1,019.21	$1,019.25	$1,019.20