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	$243.41	5.369%	$256.4787	$256.48	$256.50	$256.50
Purchase #2	$35.52	5.815%	$37.5855	$37.59	$37.60	$37.60
Purchase #3	$33.45	12.486%	$37.6266	$37.63	$37.65	$37.60
Purchase #4	$184.45	12.827%	$208.1094	$208.11	$208.10	$208.10
Purchase #5	$142.98	10.129%	$157.4624	$157.46	$157.45	$157.50
Purchase #6	$212.85	7.192%	$228.1582	$228.16	$228.15	$228.20
Purchase #7	$71.89	6.457%	$76.5319	$76.53	$76.55	$76.50
7 purchase totals =	$924.55		$1,001.9527	$1,001.96	$1,002.00	$1,002.00