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	$134.80	4.854%	$141.3432	$141.34	$141.35	$141.30
Purchase #2	$33.25	12.431%	$37.3833	$37.38	$37.40	$37.40
Purchase #3	$6.82	7.271%	$7.3159	$7.32	$7.30	$7.30
Purchase #4	$67.64	6.102%	$71.7674	$71.77	$71.75	$71.80
Purchase #5	$58.74	13.352%	$66.583	$66.58	$66.60	$66.60
Purchase #6	$194.42	3.337%	$200.9078	$200.91	$200.90	$200.90
Purchase #7	$119.40	9.632%	$130.9006	$130.90	$130.90	$130.90
7 purchase totals =	$615.07		$656.2012	$656.20	$656.20	$656.20