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	$85.77	6.810%	$91.6109	$91.61	$91.60	$91.60
Purchase #2	$114.42	7.171%	$122.6251	$122.63	$122.65	$122.60
Purchase #3	$50.42	11.315%	$56.125	$56.13	$56.15	$56.10
Purchase #4	$197.64	10.863%	$219.1096	$219.11	$219.10	$219.10
Purchase #5	$149.94	11.586%	$167.312	$167.31	$167.30	$167.30
Purchase #6	$240.37	10.459%	$265.5103	$265.51	$265.50	$265.50
Purchase #7	$205.91	10.855%	$228.2615	$228.26	$228.25	$228.30
7 purchase totals =	$1,044.47		$1,150.5544	$1,150.56	$1,150.55	$1,150.50