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	$82.94	6.487%	$88.3203	$88.32	$88.30	$88.30
Purchase #2	$35.49	4.470%	$37.0764	$37.08	$37.10	$37.10
Purchase #3	$17.50	7.364%	$18.7887	$18.79	$18.80	$18.80
Purchase #4	$126.69	12.770%	$142.8683	$142.87	$142.85	$142.90
Purchase #5	$213.89	7.351%	$229.6131	$229.61	$229.60	$229.60
Purchase #6	$183.55	13.375%	$208.0998	$208.10	$208.10	$208.10
Purchase #7	$38.69	9.561%	$42.3892	$42.39	$42.40	$42.40
7 purchase totals =	$698.75		$767.1558	$767.16	$767.15	$767.20