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	$189.52	6.829%	$202.4623	$202.46	$202.45	$202.50
Purchase #2	$107.39	4.617%	$112.3482	$112.35	$112.35	$112.30
Purchase #3	$229.78	11.789%	$256.8688	$256.87	$256.85	$256.90
Purchase #4	$234.63	12.743%	$264.5289	$264.53	$264.55	$264.50
Purchase #5	$140.50	7.365%	$150.8478	$150.85	$150.85	$150.80
Purchase #6	$24.48	11.323%	$27.2519	$27.25	$27.25	$27.30
Purchase #7	$177.49	7.568%	$190.9224	$190.92	$190.90	$190.90
7 purchase totals =	$1,103.79		$1,205.2303	$1,205.23	$1,205.20	$1,205.20