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	$160.45	3.398%	$165.9021	$165.90	$165.90	$165.90
Purchase #2	$116.78	4.581%	$122.1297	$122.13	$122.15	$122.10
Purchase #3	$210.56	13.391%	$238.7561	$238.76	$238.75	$238.80
Purchase #4	$89.48	9.716%	$98.1739	$98.17	$98.15	$98.20
Purchase #5	$13.28	4.516%	$13.8797	$13.88	$13.90	$13.90
Purchase #6	$209.56	13.644%	$238.1524	$238.15	$238.15	$238.20
Purchase #7	$147.52	13.574%	$167.5444	$167.54	$167.55	$167.50
7 purchase totals =	$947.63		$1,044.5383	$1,044.53	$1,044.55	$1,044.60