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	$69.73	9.625%	$76.4415	$76.44	$76.45	$76.40
Purchase #2	$52.91	6.271%	$56.228	$56.23	$56.25	$56.20
Purchase #3	$13.52	9.386%	$14.789	$14.79	$14.80	$14.80
Purchase #4	$248.86	5.339%	$262.1466	$262.15	$262.15	$262.10
Purchase #5	$204.61	9.434%	$223.9129	$223.91	$223.90	$223.90
Purchase #6	$89.46	9.707%	$98.1439	$98.14	$98.15	$98.10
Purchase #7	$130.81	6.644%	$139.501	$139.50	$139.50	$139.50
7 purchase totals =	$809.90		$871.1629	$871.16	$871.20	$871.00