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	$171.29	8.443%	$185.752	$185.75	$185.75	$185.80
Purchase #2	$168.84	4.139%	$175.8283	$175.83	$175.85	$175.80
Purchase #3	$73.49	7.175%	$78.7629	$78.76	$78.75	$78.80
Purchase #4	$118.83	3.787%	$123.3301	$123.33	$123.35	$123.30
Purchase #5	$35.87	6.668%	$38.2618	$38.26	$38.25	$38.30
Purchase #6	$19.97	3.183%	$20.6056	$20.61	$20.60	$20.60
Purchase #7	$5.42	12.598%	$6.1028	$6.10	$6.10	$6.10
7 purchase totals =	$593.71		$628.6435	$628.64	$628.65	$628.70