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	$140.91	12.607%	$158.6745	$158.67	$158.65	$158.70
Purchase #2	$183.27	3.260%	$189.2446	$189.24	$189.25	$189.20
Purchase #3	$64.57	12.109%	$72.3888	$72.39	$72.40	$72.40
Purchase #4	$201.26	4.850%	$211.0211	$211.02	$211.00	$211.00
Purchase #5	$75.50	10.381%	$83.3377	$83.34	$83.35	$83.30
Purchase #6	$203.49	9.744%	$223.3181	$223.32	$223.30	$223.30
Purchase #7	$113.79	8.500%	$123.4622	$123.46	$123.45	$123.50
7 purchase totals =	$982.79		$1,061.4470	$1,061.44	$1,061.40	$1,061.40