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	$119.25	6.534%	$127.0418	$127.04	$127.05	$127.00
Purchase #2	$71.59	9.416%	$78.3309	$78.33	$78.35	$78.30
Purchase #3	$88.58	11.224%	$98.5222	$98.52	$98.50	$98.50
Purchase #4	$76.93	13.265%	$87.1348	$87.13	$87.15	$87.10
Purchase #5	$182.89	3.293%	$188.9126	$188.91	$188.90	$188.90
Purchase #6	$28.50	6.772%	$30.43	$30.43	$30.45	$30.40
Purchase #7	$76.64	6.692%	$81.7687	$81.77	$81.75	$81.80
7 purchase totals =	$644.38		$692.1410	$692.13	$692.15	$692.00