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	$119.31	3.736%	$123.7674	$123.77	$123.75	$123.80
Purchase #2	$32.71	13.323%	$37.068	$37.07	$37.05	$37.10
Purchase #3	$246.60	12.150%	$276.5619	$276.56	$276.55	$276.60
Purchase #4	$140.49	10.868%	$155.7585	$155.76	$155.75	$155.80
Purchase #5	$139.55	5.785%	$147.623	$147.62	$147.60	$147.60
Purchase #6	$99.49	8.458%	$107.9049	$107.90	$107.90	$107.90
Purchase #7	$155.28	11.351%	$172.9058	$172.91	$172.90	$172.90
7 purchase totals =	$933.43		$1,021.5895	$1,021.59	$1,021.50	$1,021.70