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	$14.32	9.830%	$15.7277	$15.73	$15.75	$15.70
Purchase #2	$76.78	6.824%	$82.0195	$82.02	$82.00	$82.00
Purchase #3	$226.36	8.566%	$245.75	$245.75	$245.75	$245.80
Purchase #4	$215.93	10.533%	$238.6739	$238.67	$238.65	$238.70
Purchase #5	$136.64	11.605%	$152.4971	$152.50	$152.50	$152.50
Purchase #6	$133.83	12.500%	$150.5588	$150.56	$150.55	$150.60
Purchase #7	$133.96	13.588%	$152.1625	$152.16	$152.15	$152.20
7 purchase totals =	$937.82		$1,037.3895	$1,037.39	$1,037.35	$1,037.50