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	$150.94	4.389%	$157.5648	$157.56	$157.55	$157.60
Purchase #2	$180.80	7.653%	$194.6366	$194.64	$194.65	$194.60
Purchase #3	$79.52	5.539%	$83.9246	$83.92	$83.90	$83.90
Purchase #4	$93.77	6.493%	$99.8585	$99.86	$99.85	$99.90
Purchase #5	$30.88	13.816%	$35.1464	$35.15	$35.15	$35.10
Purchase #6	$74.28	5.321%	$78.2324	$78.23	$78.25	$78.20
Purchase #7	$148.87	12.265%	$167.1289	$167.13	$167.15	$167.10
7 purchase totals =	$759.06		$816.4922	$816.49	$816.50	$816.40