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	$119.73	10.199%	$131.9413	$131.94	$131.95	$131.90
Purchase #2	$65.57	10.503%	$72.4568	$72.46	$72.45	$72.50
Purchase #3	$231.69	5.514%	$244.4654	$244.47	$244.45	$244.50
Purchase #4	$168.32	9.416%	$184.169	$184.17	$184.15	$184.20
Purchase #5	$87.97	11.260%	$97.8754	$97.88	$97.90	$97.90
Purchase #6	$205.87	8.618%	$223.6119	$223.61	$223.60	$223.60
Purchase #7	$149.44	13.615%	$169.7863	$169.79	$169.80	$169.80
7 purchase totals =	$1,028.59		$1,124.3061	$1,124.32	$1,124.30	$1,124.40