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	$60.69	13.235%	$68.7223	$68.72	$68.70	$68.70
Purchase #2	$15.88	12.425%	$17.8531	$17.85	$17.85	$17.90
Purchase #3	$69.86	10.189%	$76.978	$76.98	$77.00	$77.00
Purchase #4	$60.83	10.423%	$67.1703	$67.17	$67.15	$67.20
Purchase #5	$204.82	3.295%	$211.5688	$211.57	$211.55	$211.60
Purchase #6	$78.27	3.258%	$80.82	$80.82	$80.80	$80.80
Purchase #7	$29.72	12.784%	$33.5194	$33.52	$33.50	$33.50
7 purchase totals =	$520.07		$556.6319	$556.63	$556.55	$556.70