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	$193.80	11.221%	$215.5463	$215.55	$215.55	$215.50
Purchase #2	$210.27	11.835%	$235.1555	$235.16	$235.15	$235.20
Purchase #3	$244.35	3.717%	$253.4325	$253.43	$253.45	$253.40
Purchase #4	$244.73	10.602%	$270.6763	$270.68	$270.70	$270.70
Purchase #5	$40.60	4.773%	$42.5378	$42.54	$42.55	$42.50
Purchase #6	$53.55	6.284%	$56.9151	$56.92	$56.90	$56.90
Purchase #7	$199.25	3.540%	$206.3035	$206.30	$206.30	$206.30
7 purchase totals =	$1,186.55		$1,280.5670	$1,280.58	$1,280.60	$1,280.50