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	$156.25	8.375%	$169.3359	$169.34	$169.35	$169.30
Purchase #2	$190.40	12.149%	$213.5317	$213.53	$213.55	$213.50
Purchase #3	$124.35	13.320%	$140.9134	$140.91	$140.90	$140.90
Purchase #4	$172.30	8.520%	$186.98	$186.98	$187.00	$187.00
Purchase #5	$148.76	7.737%	$160.2696	$160.27	$160.25	$160.30
Purchase #6	$107.77	5.582%	$113.7857	$113.79	$113.80	$113.80
Purchase #7	$179.27	11.817%	$200.4543	$200.45	$200.45	$200.50
7 purchase totals =	$1,079.10		$1,185.2706	$1,185.27	$1,185.30	$1,185.30