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	$114.69	13.359%	$130.0114	$130.01	$130.00	$130.00
Purchase #2	$219.72	3.438%	$227.274	$227.27	$227.25	$227.30
Purchase #3	$34.96	12.726%	$39.409	$39.41	$39.40	$39.40
Purchase #4	$131.56	10.599%	$145.504	$145.50	$145.50	$145.50
Purchase #5	$108.75	6.744%	$116.0841	$116.08	$116.10	$116.10
Purchase #6	$91.36	13.608%	$103.7923	$103.79	$103.80	$103.80
Purchase #7	$88.42	12.426%	$99.4071	$99.41	$99.40	$99.40
7 purchase totals =	$789.46		$861.4819	$861.47	$861.45	$861.50