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	$173.78	10.729%	$192.4249	$192.42	$192.40	$192.40
Purchase #2	$214.57	13.273%	$243.0499	$243.05	$243.05	$243.00
Purchase #3	$29.72	9.274%	$32.4762	$32.48	$32.50	$32.50
Purchase #4	$91.41	6.476%	$97.3297	$97.33	$97.35	$97.30
Purchase #5	$62.84	6.772%	$67.0955	$67.10	$67.10	$67.10
Purchase #6	$154.98	13.440%	$175.8093	$175.81	$175.80	$175.80
Purchase #7	$228.42	13.217%	$258.6103	$258.61	$258.60	$258.60
7 purchase totals =	$955.72		$1,066.7958	$1,066.80	$1,066.80	$1,066.70