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	$204.68	3.475%	$211.7926	$211.79	$211.80	$211.80
Purchase #2	$99.44	4.210%	$103.6264	$103.63	$103.65	$103.60
Purchase #3	$30.26	5.862%	$32.0338	$32.03	$32.05	$32.00
Purchase #4	$86.71	4.600%	$90.6987	$90.70	$90.70	$90.70
Purchase #5	$204.90	8.213%	$221.7284	$221.73	$221.75	$221.70
Purchase #6	$72.66	13.801%	$82.6878	$82.69	$82.70	$82.70
Purchase #7	$199.64	4.626%	$208.8753	$208.88	$208.90	$208.90
7 purchase totals =	$898.29		$951.4430	$951.45	$951.55	$951.40