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	$79.89	4.859%	$83.7719	$83.77	$83.75	$83.80
Purchase #2	$160.91	4.721%	$168.5066	$168.51	$168.50	$168.50
Purchase #3	$124.49	5.469%	$131.2984	$131.30	$131.30	$131.30
Purchase #4	$213.38	4.766%	$223.5497	$223.55	$223.55	$223.50
Purchase #5	$28.25	9.845%	$31.0312	$31.03	$31.05	$31.00
Purchase #6	$200.48	8.199%	$216.9174	$216.92	$216.90	$216.90
Purchase #7	$156.41	8.265%	$169.3373	$169.34	$169.35	$169.30
7 purchase totals =	$963.81		$1,024.4125	$1,024.42	$1,024.40	$1,024.30