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	$177.46	3.487%	$183.648	$183.65	$183.65	$183.60
Purchase #2	$88.42	13.735%	$100.5645	$100.56	$100.55	$100.60
Purchase #3	$102.28	9.824%	$112.328	$112.33	$112.35	$112.30
Purchase #4	$224.96	13.404%	$255.1136	$255.11	$255.10	$255.10
Purchase #5	$30.55	5.433%	$32.2098	$32.21	$32.20	$32.20
Purchase #6	$80.93	11.407%	$90.1617	$90.16	$90.15	$90.20
Purchase #7	$12.70	9.252%	$13.875	$13.88	$13.90	$13.90
7 purchase totals =	$717.30		$787.9006	$787.90	$787.90	$787.90