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	$77.53	10.236%	$85.466	$85.47	$85.45	$85.50
Purchase #2	$152.93	13.342%	$173.3339	$173.33	$173.35	$173.30
Purchase #3	$67.83	10.534%	$74.9752	$74.98	$75.00	$75.00
Purchase #4	$222.93	9.146%	$243.3192	$243.32	$243.30	$243.30
Purchase #5	$203.92	11.502%	$227.3749	$227.37	$227.35	$227.40
Purchase #6	$145.77	11.446%	$162.4548	$162.45	$162.45	$162.50
Purchase #7	$18.87	10.294%	$20.8125	$20.81	$20.80	$20.80
7 purchase totals =	$889.78		$987.7365	$987.73	$987.70	$987.80