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	$231.80	9.629%	$254.12	$254.12	$254.10	$254.10
Purchase #2	$128.86	8.236%	$139.4729	$139.47	$139.45	$139.50
Purchase #3	$49.32	7.279%	$52.91	$52.91	$52.90	$52.90
Purchase #4	$130.42	8.121%	$141.0114	$141.01	$141.00	$141.00
Purchase #5	$223.65	6.731%	$238.7039	$238.70	$238.70	$238.70
Purchase #6	$34.53	4.780%	$36.1805	$36.18	$36.20	$36.20
Purchase #7	$172.69	10.471%	$190.7724	$190.77	$190.75	$190.80
7 purchase totals =	$971.27		$1,053.1711	$1,053.16	$1,053.10	$1,053.20