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	$78.95	4.348%	$82.3827	$82.38	$82.40	$82.40
Purchase #2	$31.52	4.339%	$32.8877	$32.89	$32.90	$32.90
Purchase #3	$124.69	7.836%	$134.4607	$134.46	$134.45	$134.50
Purchase #4	$83.87	7.632%	$90.271	$90.27	$90.25	$90.30
Purchase #5	$108.58	11.108%	$120.6411	$120.64	$120.65	$120.60
Purchase #6	$164.88	11.194%	$183.3367	$183.34	$183.35	$183.30
Purchase #7	$65.68	6.186%	$69.743	$69.74	$69.75	$69.70
7 purchase totals =	$658.17		$713.7229	$713.72	$713.75	$713.70