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	$215.33	4.736%	$225.528	$225.53	$225.55	$225.50
Purchase #2	$112.73	13.737%	$128.2157	$128.22	$128.20	$128.20
Purchase #3	$111.32	3.184%	$114.8644	$114.86	$114.85	$114.90
Purchase #4	$46.51	7.784%	$50.1303	$50.13	$50.15	$50.10
Purchase #5	$157.50	10.213%	$173.5855	$173.59	$173.60	$173.60
Purchase #6	$249.57	7.780%	$268.9865	$268.99	$269.00	$269.00
Purchase #7	$76.98	6.744%	$82.1715	$82.17	$82.15	$82.20
7 purchase totals =	$969.94		$1,043.4819	$1,043.49	$1,043.50	$1,043.50