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	$117.99	8.743%	$128.3059	$128.31	$128.30	$128.30
Purchase #2	$82.65	13.506%	$93.8127	$93.81	$93.80	$93.80
Purchase #3	$45.82	7.788%	$49.3885	$49.39	$49.40	$49.40
Purchase #4	$147.48	4.124%	$153.5621	$153.56	$153.55	$153.60
Purchase #5	$129.59	13.478%	$147.0561	$147.06	$147.05	$147.10
Purchase #6	$249.46	13.535%	$283.2244	$283.22	$283.20	$283.20
Purchase #7	$173.28	10.569%	$191.594	$191.59	$191.60	$191.60
7 purchase totals =	$946.27		$1,046.9437	$1,046.94	$1,046.90	$1,047.00