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	$41.59	3.650%	$43.108	$43.11	$43.10	$43.10
Purchase #2	$82.51	7.837%	$88.9763	$88.98	$89.00	$89.00
Purchase #3	$118.47	5.325%	$124.7785	$124.78	$124.80	$124.80
Purchase #4	$186.96	11.668%	$208.7745	$208.77	$208.75	$208.80
Purchase #5	$35.87	4.273%	$37.4027	$37.40	$37.40	$37.40
Purchase #6	$188.46	5.808%	$199.4058	$199.41	$199.40	$199.40
Purchase #7	$198.82	11.562%	$221.8076	$221.81	$221.80	$221.80
7 purchase totals =	$852.68		$924.2534	$924.26	$924.25	$924.30