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	$95.83	12.548%	$107.8547	$107.85	$107.85	$107.90
Purchase #2	$128.83	9.557%	$141.1423	$141.14	$141.15	$141.10
Purchase #3	$83.26	8.709%	$90.5111	$90.51	$90.50	$90.50
Purchase #4	$136.85	5.296%	$144.0976	$144.10	$144.10	$144.10
Purchase #5	$53.30	9.108%	$58.1546	$58.15	$58.15	$58.20
Purchase #6	$247.56	6.791%	$264.3718	$264.37	$264.35	$264.40
Purchase #7	$198.95	11.781%	$222.3883	$222.39	$222.40	$222.40
7 purchase totals =	$944.58		$1,028.5204	$1,028.51	$1,028.50	$1,028.60