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	$100.29	11.512%	$111.8354	$111.84	$111.85	$111.80
Purchase #2	$157.67	12.577%	$177.5002	$177.50	$177.50	$177.50
Purchase #3	$145.79	9.814%	$160.0978	$160.10	$160.10	$160.10
Purchase #4	$169.63	13.224%	$192.0619	$192.06	$192.05	$192.10
Purchase #5	$185.47	4.683%	$194.1556	$194.16	$194.15	$194.20
Purchase #6	$102.86	6.276%	$109.3155	$109.32	$109.30	$109.30
Purchase #7	$64.75	11.154%	$71.9722	$71.97	$71.95	$72.00
7 purchase totals =	$926.46		$1,016.9386	$1,016.95	$1,016.90	$1,017.00