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	$61.88	7.247%	$66.3644	$66.36	$66.35	$66.40
Purchase #2	$51.67	12.803%	$58.2853	$58.29	$58.30	$58.30
Purchase #3	$242.82	13.330%	$275.1879	$275.19	$275.20	$275.20
Purchase #4	$189.26	3.686%	$196.2361	$196.24	$196.25	$196.20
Purchase #5	$163.69	12.617%	$184.3428	$184.34	$184.35	$184.30
Purchase #6	$165.49	4.468%	$172.8841	$172.88	$172.90	$172.90
Purchase #7	$220.37	11.395%	$245.4812	$245.48	$245.50	$245.50
7 purchase totals =	$1,095.18		$1,198.7818	$1,198.78	$1,198.85	$1,198.80