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	$202.31	13.760%	$230.1479	$230.15	$230.15	$230.10
Purchase #2	$87.98	8.575%	$95.5243	$95.52	$95.50	$95.50
Purchase #3	$96.52	13.329%	$109.3852	$109.39	$109.40	$109.40
Purchase #4	$113.96	11.713%	$127.3081	$127.31	$127.30	$127.30
Purchase #5	$134.89	12.216%	$151.3682	$151.37	$151.35	$151.40
Purchase #6	$42.87	12.158%	$48.0821	$48.08	$48.10	$48.10
Purchase #7	$30.36	13.799%	$34.5494	$34.55	$34.55	$34.50
7 purchase totals =	$708.89		$796.3652	$796.37	$796.35	$796.30