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	$14.76	6.807%	$15.7647	$15.76	$15.75	$15.80
Purchase #2	$118.65	7.421%	$127.455	$127.46	$127.45	$127.50
Purchase #3	$30.34	6.846%	$32.4171	$32.42	$32.40	$32.40
Purchase #4	$65.56	7.386%	$70.4023	$70.40	$70.40	$70.40
Purchase #5	$151.93	10.169%	$167.3798	$167.38	$167.40	$167.40
Purchase #6	$234.94	12.526%	$264.3686	$264.37	$264.35	$264.40
Purchase #7	$144.69	5.231%	$152.2587	$152.26	$152.25	$152.30
7 purchase totals =	$760.87		$830.0462	$830.05	$830.00	$830.20