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	$187.37	6.486%	$199.5228	$199.52	$199.50	$199.50
Purchase #2	$214.29	12.427%	$240.9198	$240.92	$240.90	$240.90
Purchase #3	$43.44	10.812%	$48.1367	$48.14	$48.15	$48.10
Purchase #4	$243.38	9.127%	$265.5933	$265.59	$265.60	$265.60
Purchase #5	$9.65	10.404%	$10.654	$10.65	$10.65	$10.70
Purchase #6	$231.57	5.192%	$243.5931	$243.59	$243.60	$243.60
Purchase #7	$162.46	12.519%	$182.7984	$182.80	$182.80	$182.80
7 purchase totals =	$1,092.16		$1,191.2181	$1,191.21	$1,191.20	$1,191.20