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	$83.37	12.823%	$94.0605	$94.06	$94.05	$94.10
Purchase #2	$141.71	4.849%	$148.5815	$148.58	$148.60	$148.60
Purchase #3	$238.56	10.601%	$263.8497	$263.85	$263.85	$263.80
Purchase #4	$124.81	10.569%	$138.0012	$138.00	$138.00	$138.00
Purchase #5	$169.31	9.792%	$185.8888	$185.89	$185.90	$185.90
Purchase #6	$218.61	7.122%	$234.1794	$234.18	$234.20	$234.20
Purchase #7	$33.74	6.645%	$35.982	$35.98	$36.00	$36.00
7 purchase totals =	$1,010.11		$1,100.5431	$1,100.54	$1,100.60	$1,100.60