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	$168.53	10.285%	$185.8633	$185.86	$185.85	$185.90
Purchase #2	$19.55	4.869%	$20.5019	$20.50	$20.50	$20.50
Purchase #3	$159.40	4.465%	$166.5172	$166.52	$166.50	$166.50
Purchase #4	$129.63	12.151%	$145.3813	$145.38	$145.40	$145.40
Purchase #5	$32.80	8.232%	$35.5001	$35.50	$35.50	$35.50
Purchase #6	$210.55	12.367%	$236.5887	$236.59	$236.60	$236.60
Purchase #7	$23.56	7.174%	$25.2502	$25.25	$25.25	$25.30
7 purchase totals =	$744.02		$815.6027	$815.60	$815.60	$815.70