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	5.337%	$182.0329	$182.03	$182.05	$182.00
Purchase #2	$186.47	6.238%	$198.102	$198.10	$198.10	$198.10
Purchase #3	$123.96	7.675%	$133.4739	$133.47	$133.45	$133.50
Purchase #4	$196.92	11.771%	$220.0995	$220.10	$220.10	$220.10
Purchase #5	$166.64	13.478%	$189.0997	$189.10	$189.10	$189.10
Purchase #6	$55.80	4.172%	$58.128	$58.13	$58.15	$58.10
Purchase #7	$249.86	10.321%	$275.6481	$275.65	$275.65	$275.60
7 purchase totals =	$1,152.46		$1,256.5841	$1,256.58	$1,256.60	$1,256.50