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	$157.69	13.632%	$179.1863	$179.19	$179.20	$179.20
Purchase #2	$61.29	4.197%	$63.8623	$63.86	$63.85	$63.90
Purchase #3	$126.74	11.567%	$141.4	$141.40	$141.40	$141.40
Purchase #4	$121.77	7.131%	$130.4534	$130.45	$130.45	$130.50
Purchase #5	$238.27	11.126%	$264.7799	$264.78	$264.80	$264.80
Purchase #6	$33.96	12.665%	$38.261	$38.26	$38.25	$38.30
Purchase #7	$163.40	13.151%	$184.8887	$184.89	$184.90	$184.90
7 purchase totals =	$903.12		$1,002.8316	$1,002.83	$1,002.85	$1,003.00