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	$53.94	13.374%	$61.1539	$61.15	$61.15	$61.20
Purchase #2	$42.86	5.310%	$45.1359	$45.14	$45.15	$45.10
Purchase #3	$171.78	8.621%	$186.5892	$186.59	$186.60	$186.60
Purchase #4	$233.30	10.818%	$258.5384	$258.54	$258.55	$258.50
Purchase #5	$91.84	8.648%	$99.7823	$99.78	$99.80	$99.80
Purchase #6	$83.52	3.208%	$86.1993	$86.20	$86.20	$86.20
Purchase #7	$244.86	12.150%	$274.6105	$274.61	$274.60	$274.60
7 purchase totals =	$922.10		$1,012.0095	$1,012.01	$1,012.05	$1,012.00