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	$142.89	4.873%	$149.853	$149.85	$149.85	$149.90
Purchase #2	$87.75	13.714%	$99.784	$99.78	$99.80	$99.80
Purchase #3	$75.35	4.163%	$78.4868	$78.49	$78.50	$78.50
Purchase #4	$78.52	3.545%	$81.3035	$81.30	$81.30	$81.30
Purchase #5	$165.85	7.421%	$178.1577	$178.16	$178.15	$178.20
Purchase #6	$77.43	4.462%	$80.8849	$80.88	$80.90	$80.90
Purchase #7	$174.30	9.199%	$190.3339	$190.33	$190.35	$190.30
7 purchase totals =	$802.09		$858.8038	$858.79	$858.85	$858.90