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	$208.78	3.281%	$215.6301	$215.63	$215.65	$215.60
Purchase #2	$28.96	4.731%	$30.3301	$30.33	$30.35	$30.30
Purchase #3	$186.42	5.643%	$196.9397	$196.94	$196.95	$196.90
Purchase #4	$83.51	8.155%	$90.3202	$90.32	$90.30	$90.30
Purchase #5	$119.73	10.822%	$132.6872	$132.69	$132.70	$132.70
Purchase #6	$88.95	10.200%	$98.0229	$98.02	$98.00	$98.00
Purchase #7	$82.95	5.399%	$87.4285	$87.43	$87.45	$87.40
7 purchase totals =	$799.30		$851.3587	$851.36	$851.40	$851.20