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	$188.34	12.688%	$212.2366	$212.24	$212.25	$212.20
Purchase #2	$65.86	13.731%	$74.9032	$74.90	$74.90	$74.90
Purchase #3	$137.30	12.327%	$154.225	$154.23	$154.25	$154.20
Purchase #4	$87.50	9.852%	$96.1205	$96.12	$96.10	$96.10
Purchase #5	$87.32	9.773%	$95.8538	$95.85	$95.85	$95.90
Purchase #6	$155.78	5.848%	$164.89	$164.89	$164.90	$164.90
Purchase #7	$239.31	13.412%	$271.4063	$271.41	$271.40	$271.40
7 purchase totals =	$961.41		$1,069.6354	$1,069.64	$1,069.65	$1,069.60