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	$151.65	13.349%	$171.8938	$171.89	$171.90	$171.90
Purchase #2	$246.59	11.493%	$274.9306	$274.93	$274.95	$274.90
Purchase #3	$70.72	10.238%	$77.9603	$77.96	$77.95	$78.00
Purchase #4	$207.28	4.120%	$215.8199	$215.82	$215.80	$215.80
Purchase #5	$154.51	9.501%	$169.19	$169.19	$169.20	$169.20
Purchase #6	$39.44	7.790%	$42.5124	$42.51	$42.50	$42.50
Purchase #7	$84.81	12.117%	$95.0864	$95.09	$95.10	$95.10
7 purchase totals =	$955.00		$1,047.3934	$1,047.39	$1,047.40	$1,047.40