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	$184.79	6.287%	$196.4077	$196.41	$196.40	$196.40
Purchase #2	$137.63	5.250%	$144.8556	$144.86	$144.85	$144.90
Purchase #3	$218.87	10.806%	$242.5211	$242.52	$242.50	$242.50
Purchase #4	$44.96	6.753%	$47.9961	$48.00	$48.00	$48.00
Purchase #5	$159.85	12.832%	$180.362	$180.36	$180.35	$180.40
Purchase #6	$184.54	12.777%	$208.1187	$208.12	$208.10	$208.10
Purchase #7	$214.98	12.581%	$242.0266	$242.03	$242.05	$242.00
7 purchase totals =	$1,145.62		$1,262.2878	$1,262.30	$1,262.25	$1,262.30