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	$81.66	9.868%	$89.7182	$89.72	$89.70	$89.70
Purchase #2	$78.51	5.103%	$82.5164	$82.52	$82.50	$82.50
Purchase #3	$242.75	5.798%	$256.8246	$256.82	$256.80	$256.80
Purchase #4	$102.32	8.187%	$110.6969	$110.70	$110.70	$110.70
Purchase #5	$223.57	8.751%	$243.1346	$243.13	$243.15	$243.10
Purchase #6	$210.75	12.274%	$236.6175	$236.62	$236.60	$236.60
Purchase #7	$31.99	12.153%	$35.8777	$35.88	$35.90	$35.90
7 purchase totals =	$971.55		$1,055.3859	$1,055.39	$1,055.35	$1,055.30