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	$90.64	11.388%	$100.9621	$100.96	$100.95	$101.00
Purchase #2	$183.36	10.189%	$202.0426	$202.04	$202.05	$202.00
Purchase #3	$248.89	6.489%	$265.0405	$265.04	$265.05	$265.00
Purchase #4	$30.85	4.680%	$32.2938	$32.29	$32.30	$32.30
Purchase #5	$56.60	4.523%	$59.16	$59.16	$59.15	$59.20
Purchase #6	$160.62	7.637%	$172.8865	$172.89	$172.90	$172.90
Purchase #7	$171.52	10.270%	$189.1351	$189.14	$189.15	$189.10
7 purchase totals =	$942.48		$1,021.5206	$1,021.52	$1,021.55	$1,021.50