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	$120.53	5.269%	$126.8807	$126.88	$126.90	$126.90
Purchase #2	$248.89	9.384%	$272.2458	$272.25	$272.25	$272.20
Purchase #3	$79.56	6.425%	$84.6717	$84.67	$84.65	$84.70
Purchase #4	$128.34	10.263%	$141.5115	$141.51	$141.50	$141.50
Purchase #5	$136.45	3.415%	$141.1098	$141.11	$141.10	$141.10
Purchase #6	$144.61	10.649%	$160.0095	$160.01	$160.00	$160.00
Purchase #7	$108.27	10.385%	$119.5138	$119.51	$119.50	$119.50
7 purchase totals =	$966.65		$1,045.9428	$1,045.94	$1,045.90	$1,045.90