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	$172.81	5.757%	$182.7587	$182.76	$182.75	$182.80
Purchase #2	$84.44	9.155%	$92.1705	$92.17	$92.15	$92.20
Purchase #3	$215.43	11.121%	$239.388	$239.39	$239.40	$239.40
Purchase #4	$44.58	11.717%	$49.8034	$49.80	$49.80	$49.80
Purchase #5	$182.50	3.404%	$188.7123	$188.71	$188.70	$188.70
Purchase #6	$246.86	10.447%	$272.6495	$272.65	$272.65	$272.60
Purchase #7	$75.27	13.636%	$85.5338	$85.53	$85.55	$85.50
7 purchase totals =	$1,021.89		$1,111.0162	$1,111.01	$1,111.00	$1,111.00