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	$50.64	11.108%	$56.2651	$56.27	$56.25	$56.30
Purchase #2	$152.29	5.649%	$160.8929	$160.89	$160.90	$160.90
Purchase #3	$24.83	9.787%	$27.2601	$27.26	$27.25	$27.30
Purchase #4	$246.53	5.853%	$260.9594	$260.96	$260.95	$261.00
Purchase #5	$147.43	6.778%	$157.4228	$157.42	$157.40	$157.40
Purchase #6	$156.50	3.601%	$162.1356	$162.14	$162.15	$162.10
Purchase #7	$176.82	8.110%	$191.1601	$191.16	$191.15	$191.20
7 purchase totals =	$955.04		$1,016.0960	$1,016.10	$1,016.05	$1,016.20