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	$144.27	6.372%	$153.4629	$153.46	$153.45	$153.50
Purchase #2	$174.70	5.795%	$184.8239	$184.82	$184.80	$184.80
Purchase #3	$95.33	8.740%	$103.6618	$103.66	$103.65	$103.70
Purchase #4	$87.73	10.190%	$96.6697	$96.67	$96.65	$96.70
Purchase #5	$169.59	11.797%	$189.5965	$189.60	$189.60	$189.60
Purchase #6	$67.45	6.720%	$71.9826	$71.98	$72.00	$72.00
Purchase #7	$250.42	3.495%	$259.1722	$259.17	$259.15	$259.20
7 purchase totals =	$989.49		$1,059.3696	$1,059.36	$1,059.30	$1,059.50