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	$98.33	3.173%	$101.45	$101.45	$101.45	$101.50
Purchase #2	$87.84	13.327%	$99.5464	$99.55	$99.55	$99.50
Purchase #3	$159.70	7.691%	$171.9825	$171.98	$172.00	$172.00
Purchase #4	$57.86	10.375%	$63.863	$63.86	$63.85	$63.90
Purchase #5	$111.71	9.671%	$122.5135	$122.51	$122.50	$122.50
Purchase #6	$55.31	12.309%	$62.1181	$62.12	$62.10	$62.10
Purchase #7	$210.42	8.216%	$227.7081	$227.71	$227.70	$227.70
7 purchase totals =	$781.17		$849.1816	$849.18	$849.15	$849.20