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	$148.54	10.480%	$164.107	$164.11	$164.10	$164.10
Purchase #2	$179.63	9.609%	$196.8906	$196.89	$196.90	$196.90
Purchase #3	$231.30	5.840%	$244.8079	$244.81	$244.80	$244.80
Purchase #4	$36.44	12.108%	$40.8522	$40.85	$40.85	$40.90
Purchase #5	$14.36	8.523%	$15.5839	$15.58	$15.60	$15.60
Purchase #6	$56.88	9.265%	$62.1499	$62.15	$62.15	$62.10
Purchase #7	$95.33	9.168%	$104.0699	$104.07	$104.05	$104.10
7 purchase totals =	$762.48		$828.4614	$828.46	$828.45	$828.50