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	$160.96	7.266%	$172.6554	$172.66	$172.65	$172.70
Purchase #2	$214.41	4.726%	$224.543	$224.54	$224.55	$224.50
Purchase #3	$144.41	5.258%	$152.0031	$152.00	$152.00	$152.00
Purchase #4	$186.94	11.744%	$208.8942	$208.89	$208.90	$208.90
Purchase #5	$90.98	13.282%	$103.064	$103.06	$103.05	$103.10
Purchase #6	$125.69	12.435%	$141.3196	$141.32	$141.30	$141.30
Purchase #7	$139.35	10.683%	$154.2368	$154.24	$154.25	$154.20
7 purchase totals =	$1,062.74		$1,156.7161	$1,156.71	$1,156.70	$1,156.70