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	$35.58	5.799%	$37.6433	$37.64	$37.65	$37.60
Purchase #2	$230.86	7.127%	$247.3134	$247.31	$247.30	$247.30
Purchase #3	$165.32	10.557%	$182.7728	$182.77	$182.75	$182.80
Purchase #4	$157.88	6.603%	$168.3048	$168.30	$168.30	$168.30
Purchase #5	$199.57	3.526%	$206.6068	$206.61	$206.60	$206.60
Purchase #6	$99.98	11.833%	$111.8106	$111.81	$111.80	$111.80
Purchase #7	$38.99	6.690%	$41.5984	$41.60	$41.60	$41.60
7 purchase totals =	$928.18		$996.0501	$996.04	$996.00	$996.00