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	$82.67	4.627%	$86.4951	$86.50	$86.50	$86.50
Purchase #2	$216.60	12.273%	$243.1833	$243.18	$243.20	$243.20
Purchase #3	$223.85	3.321%	$231.2841	$231.28	$231.30	$231.30
Purchase #4	$98.26	7.102%	$105.2384	$105.24	$105.25	$105.20
Purchase #5	$66.39	8.213%	$71.8426	$71.84	$71.85	$71.80
Purchase #6	$140.88	7.271%	$151.1234	$151.12	$151.10	$151.10
Purchase #7	$103.38	10.243%	$113.9692	$113.97	$113.95	$114.00
7 purchase totals =	$932.03		$1,003.1361	$1,003.13	$1,003.15	$1,003.10