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	$216.27	9.816%	$237.4991	$237.50	$237.50	$237.50
Purchase #2	$99.60	11.582%	$111.1357	$111.14	$111.15	$111.10
Purchase #3	$88.66	6.368%	$94.3059	$94.31	$94.30	$94.30
Purchase #4	$163.89	3.372%	$169.4164	$169.42	$169.40	$169.40
Purchase #5	$160.62	7.649%	$172.9058	$172.91	$172.90	$172.90
Purchase #6	$115.33	3.598%	$119.4796	$119.48	$119.50	$119.50
Purchase #7	$22.97	4.598%	$24.0262	$24.03	$24.05	$24.00
7 purchase totals =	$867.34		$928.7687	$928.79	$928.80	$928.70