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	$121.93	8.665%	$132.4952	$132.50	$132.50	$132.50
Purchase #2	$234.38	13.349%	$265.6674	$265.67	$265.65	$265.70
Purchase #3	$83.60	6.539%	$89.0666	$89.07	$89.05	$89.10
Purchase #4	$244.38	7.769%	$263.3659	$263.37	$263.35	$263.40
Purchase #5	$101.77	7.527%	$109.4302	$109.43	$109.45	$109.40
Purchase #6	$11.46	5.704%	$12.1137	$12.11	$12.10	$12.10
Purchase #7	$238.47	7.473%	$256.2909	$256.29	$256.30	$256.30
7 purchase totals =	$1,035.99		$1,128.4299	$1,128.44	$1,128.40	$1,128.50