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	$238.29	3.127%	$245.7413	$245.74	$245.75	$245.70
Purchase #2	$171.34	8.408%	$185.7463	$185.75	$185.75	$185.70
Purchase #3	$120.64	5.654%	$127.461	$127.46	$127.45	$127.50
Purchase #4	$50.32	5.183%	$52.9281	$52.93	$52.95	$52.90
Purchase #5	$80.94	8.380%	$87.7228	$87.72	$87.70	$87.70
Purchase #6	$48.82	7.819%	$52.6372	$52.64	$52.65	$52.60
Purchase #7	$47.95	12.184%	$53.7922	$53.79	$53.80	$53.80
7 purchase totals =	$758.30		$806.0289	$806.03	$806.05	$805.90