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	$163.80	10.373%	$180.791	$180.79	$180.80	$180.80
Purchase #2	$61.85	5.433%	$65.2103	$65.21	$65.20	$65.20
Purchase #3	$229.73	5.601%	$242.5972	$242.60	$242.60	$242.60
Purchase #4	$158.61	13.206%	$179.556	$179.56	$179.55	$179.60
Purchase #5	$31.83	11.687%	$35.55	$35.55	$35.55	$35.60
Purchase #6	$202.59	8.128%	$219.0565	$219.06	$219.05	$219.10
Purchase #7	$231.91	5.862%	$245.5046	$245.50	$245.50	$245.50
7 purchase totals =	$1,080.32		$1,168.2656	$1,168.27	$1,168.25	$1,168.40