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	$55.83	7.183%	$59.8403	$59.84	$59.85	$59.80
Purchase #2	$9.96	4.584%	$10.4166	$10.42	$10.40	$10.40
Purchase #3	$87.56	12.280%	$98.3124	$98.31	$98.30	$98.30
Purchase #4	$38.84	11.123%	$43.1602	$43.16	$43.15	$43.20
Purchase #5	$58.49	8.708%	$63.5833	$63.58	$63.60	$63.60
Purchase #6	$211.34	7.512%	$227.2159	$227.22	$227.20	$227.20
Purchase #7	$165.37	12.615%	$186.2314	$186.23	$186.25	$186.20
7 purchase totals =	$627.39		$688.7601	$688.76	$688.75	$688.70