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	$33.82	8.612%	$36.7326	$36.73	$36.75	$36.70
Purchase #2	$73.60	13.321%	$83.4043	$83.40	$83.40	$83.40
Purchase #3	$113.77	10.313%	$125.5031	$125.50	$125.50	$125.50
Purchase #4	$86.40	11.644%	$96.4604	$96.46	$96.45	$96.50
Purchase #5	$165.94	6.591%	$176.8771	$176.88	$176.90	$176.90
Purchase #6	$123.79	6.310%	$131.6011	$131.60	$131.60	$131.60
Purchase #7	$119.41	9.838%	$131.1576	$131.16	$131.15	$131.20
7 purchase totals =	$716.73		$781.7362	$781.73	$781.75	$781.80