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	$198.53	11.120%	$220.6065	$220.61	$220.60	$220.60
Purchase #2	$108.77	10.598%	$120.2974	$120.30	$120.30	$120.30
Purchase #3	$170.87	10.596%	$188.9754	$188.98	$189.00	$189.00
Purchase #4	$123.26	13.800%	$140.2699	$140.27	$140.25	$140.30
Purchase #5	$38.31	8.222%	$41.4598	$41.46	$41.45	$41.50
Purchase #6	$96.29	7.771%	$103.7727	$103.77	$103.75	$103.80
Purchase #7	$179.29	4.807%	$187.9085	$187.91	$187.90	$187.90
7 purchase totals =	$915.32		$1,003.2902	$1,003.30	$1,003.25	$1,003.40