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	$36.71	5.856%	$38.8597	$38.86	$38.85	$38.90
Purchase #2	$239.94	13.143%	$271.4753	$271.48	$271.50	$271.50
Purchase #3	$216.41	10.292%	$238.6829	$238.68	$238.70	$238.70
Purchase #4	$145.78	13.607%	$165.6163	$165.62	$165.60	$165.60
Purchase #5	$131.64	9.777%	$144.5104	$144.51	$144.50	$144.50
Purchase #6	$80.60	11.272%	$89.6852	$89.69	$89.70	$89.70
Purchase #7	$90.34	9.642%	$99.0506	$99.05	$99.05	$99.10
7 purchase totals =	$941.42		$1,047.8804	$1,047.89	$1,047.90	$1,048.00