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	$33.67	5.206%	$35.4229	$35.42	$35.40	$35.40
Purchase #2	$76.71	11.720%	$85.7004	$85.70	$85.70	$85.70
Purchase #3	$98.70	12.781%	$111.3148	$111.31	$111.30	$111.30
Purchase #4	$73.51	4.682%	$76.9517	$76.95	$76.95	$77.00
Purchase #5	$35.28	5.335%	$37.1622	$37.16	$37.15	$37.20
Purchase #6	$5.59	5.271%	$5.8846	$5.88	$5.90	$5.90
Purchase #7	$230.46	6.437%	$245.2947	$245.29	$245.30	$245.30
7 purchase totals =	$553.92		$597.7313	$597.71	$597.70	$597.80