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	$88.72	10.723%	$98.2334	$98.23	$98.25	$98.20
Purchase #2	$242.30	10.241%	$267.1139	$267.11	$267.10	$267.10
Purchase #3	$248.26	13.425%	$281.5889	$281.59	$281.60	$281.60
Purchase #4	$129.25	11.539%	$144.1642	$144.16	$144.15	$144.20
Purchase #5	$39.90	9.258%	$43.5939	$43.59	$43.60	$43.60
Purchase #6	$159.29	6.179%	$169.1325	$169.13	$169.15	$169.10
Purchase #7	$61.34	7.521%	$65.9534	$65.95	$65.95	$66.00
7 purchase totals =	$969.06		$1,069.7802	$1,069.76	$1,069.80	$1,069.80