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	$114.87	6.832%	$122.7179	$122.72	$122.70	$122.70
Purchase #2	$94.44	13.411%	$107.1053	$107.11	$107.10	$107.10
Purchase #3	$187.82	6.539%	$200.1015	$200.10	$200.10	$200.10
Purchase #4	$245.47	12.204%	$275.4272	$275.43	$275.45	$275.40
Purchase #5	$170.78	3.285%	$176.3901	$176.39	$176.40	$176.40
Purchase #6	$135.48	11.481%	$151.0345	$151.03	$151.05	$151.00
Purchase #7	$69.73	13.123%	$78.8807	$78.88	$78.90	$78.90
7 purchase totals =	$1,018.59		$1,111.6572	$1,111.66	$1,111.70	$1,111.60