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	$217.28	11.557%	$242.391	$242.39	$242.40	$242.40
Purchase #2	$162.62	3.104%	$167.6677	$167.67	$167.65	$167.70
Purchase #3	$31.79	10.184%	$35.0275	$35.03	$35.05	$35.00
Purchase #4	$112.89	9.283%	$123.3696	$123.37	$123.35	$123.40
Purchase #5	$148.27	13.593%	$168.4243	$168.42	$168.40	$168.40
Purchase #6	$180.79	10.138%	$199.1185	$199.12	$199.10	$199.10
Purchase #7	$159.82	13.667%	$181.6626	$181.66	$181.65	$181.70
7 purchase totals =	$1,013.46		$1,117.6612	$1,117.66	$1,117.60	$1,117.70