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	$115.53	10.418%	$127.5659	$127.57	$127.55	$127.60
Purchase #2	$80.81	4.443%	$84.4004	$84.40	$84.40	$84.40
Purchase #3	$63.83	13.828%	$72.6564	$72.66	$72.65	$72.70
Purchase #4	$92.35	7.279%	$99.0722	$99.07	$99.05	$99.10
Purchase #5	$88.25	9.796%	$96.895	$96.90	$96.90	$96.90
Purchase #6	$6.53	3.833%	$6.7803	$6.78	$6.80	$6.80
Purchase #7	$111.86	5.234%	$117.7148	$117.71	$117.70	$117.70
7 purchase totals =	$559.16		$605.0850	$605.09	$605.05	$605.20