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	$160.89	4.702%	$168.455	$168.46	$168.45	$168.50
Purchase #2	$165.52	4.678%	$173.263	$173.26	$173.25	$173.30
Purchase #3	$161.73	5.794%	$171.1006	$171.10	$171.10	$171.10
Purchase #4	$79.79	4.220%	$83.1571	$83.16	$83.15	$83.20
Purchase #5	$11.76	4.698%	$12.3125	$12.31	$12.30	$12.30
Purchase #6	$230.28	7.457%	$247.452	$247.45	$247.45	$247.50
Purchase #7	$220.53	6.606%	$235.0982	$235.10	$235.10	$235.10
7 purchase totals =	$1,030.50		$1,090.8384	$1,090.84	$1,090.80	$1,091.00