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	$6.35	11.795%	$7.099	$7.10	$7.10	$7.10
Purchase #2	$105.48	5.342%	$111.1147	$111.11	$111.10	$111.10
Purchase #3	$160.55	7.523%	$172.6282	$172.63	$172.65	$172.60
Purchase #4	$167.65	4.406%	$175.0367	$175.04	$175.05	$175.00
Purchase #5	$142.80	4.260%	$148.8833	$148.88	$148.90	$148.90
Purchase #6	$12.81	4.117%	$13.3374	$13.34	$13.35	$13.30
Purchase #7	$233.27	4.299%	$243.2983	$243.30	$243.30	$243.30
7 purchase totals =	$828.91		$871.3976	$871.40	$871.45	$871.30