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	$98.49	3.199%	$101.6407	$101.64	$101.65	$101.60
Purchase #2	$16.96	11.323%	$18.8804	$18.88	$18.90	$18.90
Purchase #3	$199.40	8.524%	$216.3969	$216.40	$216.40	$216.40
Purchase #4	$213.83	9.328%	$233.7761	$233.78	$233.80	$233.80
Purchase #5	$208.75	7.158%	$223.6923	$223.69	$223.70	$223.70
Purchase #6	$139.39	5.226%	$146.6745	$146.67	$146.65	$146.70
Purchase #7	$143.25	13.397%	$162.4412	$162.44	$162.45	$162.40
7 purchase totals =	$1,020.07		$1,103.5021	$1,103.50	$1,103.55	$1,103.50