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	$80.28	11.712%	$89.6824	$89.68	$89.70	$89.70
Purchase #2	$126.87	11.575%	$141.5552	$141.56	$141.55	$141.60
Purchase #3	$184.85	8.152%	$199.919	$199.92	$199.90	$199.90
Purchase #4	$57.90	3.398%	$59.8674	$59.87	$59.85	$59.90
Purchase #5	$116.80	6.171%	$124.0077	$124.01	$124.00	$124.00
Purchase #6	$150.74	8.242%	$163.164	$163.16	$163.15	$163.20
Purchase #7	$230.78	7.345%	$247.7308	$247.73	$247.75	$247.70
7 purchase totals =	$948.22		$1,025.9265	$1,025.93	$1,025.90	$1,026.00