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	$202.31	6.490%	$215.4399	$215.44	$215.45	$215.40
Purchase #2	$117.88	7.771%	$127.0405	$127.04	$127.05	$127.00
Purchase #3	$238.39	11.477%	$265.75	$265.75	$265.75	$265.80
Purchase #4	$240.43	6.128%	$255.1636	$255.16	$255.15	$255.20
Purchase #5	$214.80	3.671%	$222.6853	$222.69	$222.70	$222.70
Purchase #6	$128.28	9.107%	$139.9625	$139.96	$139.95	$140.00
Purchase #7	$135.25	13.178%	$153.0732	$153.07	$153.05	$153.10
7 purchase totals =	$1,277.34		$1,379.1150	$1,379.11	$1,379.10	$1,379.20