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	$145.39	4.215%	$151.5182	$151.52	$151.50	$151.50
Purchase #2	$121.76	3.212%	$125.6709	$125.67	$125.65	$125.70
Purchase #3	$92.88	7.805%	$100.1293	$100.13	$100.15	$100.10
Purchase #4	$248.49	12.598%	$279.7948	$279.79	$279.80	$279.80
Purchase #5	$55.49	3.464%	$57.4122	$57.41	$57.40	$57.40
Purchase #6	$109.55	9.422%	$119.8718	$119.87	$119.85	$119.90
Purchase #7	$153.81	13.874%	$175.1496	$175.15	$175.15	$175.10
7 purchase totals =	$927.37		$1,009.5468	$1,009.54	$1,009.50	$1,009.50