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	$130.46	10.703%	$144.4231	$144.42	$144.40	$144.40
Purchase #2	$168.76	11.646%	$188.4138	$188.41	$188.40	$188.40
Purchase #3	$37.32	3.205%	$38.5161	$38.52	$38.50	$38.50
Purchase #4	$49.32	5.693%	$52.1278	$52.13	$52.15	$52.10
Purchase #5	$231.52	7.510%	$248.9072	$248.91	$248.90	$248.90
Purchase #6	$95.28	10.204%	$105.0024	$105.00	$105.00	$105.00
Purchase #7	$137.79	5.487%	$145.3505	$145.35	$145.35	$145.40
7 purchase totals =	$850.45		$922.7409	$922.74	$922.70	$922.70