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	$172.82	5.821%	$182.8799	$182.88	$182.90	$182.90
Purchase #2	$108.83	10.390%	$120.1374	$120.14	$120.15	$120.10
Purchase #3	$22.97	8.357%	$24.8896	$24.89	$24.90	$24.90
Purchase #4	$100.81	11.254%	$112.1552	$112.16	$112.15	$112.20
Purchase #5	$139.43	4.516%	$145.7267	$145.73	$145.75	$145.70
Purchase #6	$250.88	13.708%	$285.2706	$285.27	$285.25	$285.30
Purchase #7	$218.66	12.155%	$245.2381	$245.24	$245.25	$245.20
7 purchase totals =	$1,014.40		$1,116.2975	$1,116.31	$1,116.35	$1,116.30