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	$65.55	8.578%	$71.1729	$71.17	$71.15	$71.20
Purchase #2	$181.86	12.432%	$204.4688	$204.47	$204.45	$204.50
Purchase #3	$24.89	10.465%	$27.4947	$27.49	$27.50	$27.50
Purchase #4	$54.52	9.237%	$59.556	$59.56	$59.55	$59.60
Purchase #5	$78.90	8.744%	$85.799	$85.80	$85.80	$85.80
Purchase #6	$209.83	8.187%	$227.0088	$227.01	$227.00	$227.00
Purchase #7	$102.50	13.782%	$116.6266	$116.63	$116.65	$116.60
7 purchase totals =	$718.05		$792.1268	$792.13	$792.10	$792.20