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	$10.88	11.187%	$12.0971	$12.10	$12.10	$12.10
Purchase #2	$168.69	13.404%	$191.3012	$191.30	$191.30	$191.30
Purchase #3	$131.59	11.195%	$146.3215	$146.32	$146.30	$146.30
Purchase #4	$85.47	7.474%	$91.858	$91.86	$91.85	$91.90
Purchase #5	$214.38	4.278%	$223.5512	$223.55	$223.55	$223.60
Purchase #6	$157.77	7.532%	$169.6532	$169.65	$169.65	$169.70
Purchase #7	$249.39	13.569%	$283.2297	$283.23	$283.25	$283.20
7 purchase totals =	$1,018.17		$1,118.0119	$1,118.01	$1,118.00	$1,118.10