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	$233.31	6.272%	$247.9432	$247.94	$247.95	$247.90
Purchase #2	$48.35	7.322%	$51.8902	$51.89	$51.90	$51.90
Purchase #3	$220.43	10.856%	$244.3599	$244.36	$244.35	$244.40
Purchase #4	$44.53	11.166%	$49.5022	$49.50	$49.50	$49.50
Purchase #5	$153.47	4.785%	$160.8135	$160.81	$160.80	$160.80
Purchase #6	$72.75	7.646%	$78.3125	$78.31	$78.30	$78.30
Purchase #7	$177.45	5.142%	$186.5745	$186.57	$186.55	$186.60
7 purchase totals =	$950.29		$1,019.3960	$1,019.38	$1,019.35	$1,019.40