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	$68.79	4.807%	$72.0967	$72.10	$72.10	$72.10
Purchase #2	$104.41	8.861%	$113.6618	$113.66	$113.65	$113.70
Purchase #3	$52.97	12.394%	$59.5351	$59.54	$59.55	$59.50
Purchase #4	$44.66	4.735%	$46.7747	$46.77	$46.75	$46.80
Purchase #5	$60.99	7.334%	$65.463	$65.46	$65.45	$65.50
Purchase #6	$51.56	7.259%	$55.3027	$55.30	$55.30	$55.30
Purchase #7	$152.86	10.780%	$169.3383	$169.34	$169.35	$169.30
7 purchase totals =	$536.24		$582.1723	$582.17	$582.15	$582.20