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	$10.32	4.221%	$10.7556	$10.76	$10.75	$10.80
Purchase #2	$74.73	4.661%	$78.2132	$78.21	$78.20	$78.20
Purchase #3	$172.33	10.487%	$190.4022	$190.40	$190.40	$190.40
Purchase #4	$77.67	13.849%	$88.4265	$88.43	$88.45	$88.40
Purchase #5	$147.60	13.528%	$167.5673	$167.57	$167.55	$167.60
Purchase #6	$72.76	11.516%	$81.139	$81.14	$81.15	$81.10
Purchase #7	$127.28	5.330%	$134.064	$134.06	$134.05	$134.10
7 purchase totals =	$682.69		$750.5678	$750.57	$750.55	$750.60