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	$143.71	5.532%	$151.66	$151.66	$151.65	$151.70
Purchase #2	$135.52	11.251%	$150.7674	$150.77	$150.75	$150.80
Purchase #3	$44.77	9.343%	$48.9529	$48.95	$48.95	$49.00
Purchase #4	$98.88	10.775%	$109.5343	$109.53	$109.55	$109.50
Purchase #5	$189.25	6.149%	$200.887	$200.89	$200.90	$200.90
Purchase #6	$239.85	5.652%	$253.4063	$253.41	$253.40	$253.40
Purchase #7	$42.85	5.425%	$45.1746	$45.17	$45.15	$45.20
7 purchase totals =	$894.83		$960.3825	$960.38	$960.35	$960.50