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	$150.97	9.433%	$165.211	$165.21	$165.20	$165.20
Purchase #2	$167.88	4.632%	$175.6562	$175.66	$175.65	$175.70
Purchase #3	$80.35	11.817%	$89.845	$89.85	$89.85	$89.80
Purchase #4	$201.99	10.338%	$222.8717	$222.87	$222.85	$222.90
Purchase #5	$74.86	3.102%	$77.1822	$77.18	$77.20	$77.20
Purchase #6	$66.80	7.194%	$71.6056	$71.61	$71.60	$71.60
Purchase #7	$197.53	7.645%	$212.6312	$212.63	$212.65	$212.60
7 purchase totals =	$940.38		$1,015.0029	$1,015.01	$1,015.00	$1,015.00