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	$92.71	10.674%	$102.6059	$102.61	$102.60	$102.60
Purchase #2	$58.56	13.350%	$66.3778	$66.38	$66.40	$66.40
Purchase #3	$129.55	3.626%	$134.2475	$134.25	$134.25	$134.20
Purchase #4	$7.47	6.666%	$7.968	$7.97	$7.95	$8.00
Purchase #5	$230.63	3.586%	$238.9004	$238.90	$238.90	$238.90
Purchase #6	$176.41	11.554%	$196.7924	$196.79	$196.80	$196.80
Purchase #7	$232.69	13.700%	$264.5685	$264.57	$264.55	$264.60
7 purchase totals =	$928.02		$1,011.4605	$1,011.47	$1,011.45	$1,011.50