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	$190.76	11.164%	$212.0564	$212.06	$212.05	$212.10
Purchase #2	$55.46	7.387%	$59.5568	$59.56	$59.55	$59.60
Purchase #3	$137.52	4.517%	$143.7318	$143.73	$143.75	$143.70
Purchase #4	$75.64	7.227%	$81.1065	$81.11	$81.10	$81.10
Purchase #5	$74.37	4.812%	$77.9487	$77.95	$77.95	$77.90
Purchase #6	$191.52	4.635%	$200.397	$200.40	$200.40	$200.40
Purchase #7	$139.52	3.483%	$144.3795	$144.38	$144.40	$144.40
7 purchase totals =	$864.79		$919.1767	$919.19	$919.20	$919.20