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	$86.51	7.372%	$92.8875	$92.89	$92.90	$92.90
Purchase #2	$158.70	8.563%	$172.2895	$172.29	$172.30	$172.30
Purchase #3	$188.67	13.722%	$214.5593	$214.56	$214.55	$214.60
Purchase #4	$40.48	6.838%	$43.248	$43.25	$43.25	$43.20
Purchase #5	$184.91	5.309%	$194.7269	$194.73	$194.75	$194.70
Purchase #6	$151.45	3.356%	$156.5327	$156.53	$156.55	$156.50
Purchase #7	$188.45	9.356%	$206.0814	$206.08	$206.10	$206.10
7 purchase totals =	$999.17		$1,080.3253	$1,080.33	$1,080.40	$1,080.30