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	$37.35	11.222%	$41.5414	$41.54	$41.55	$41.50
Purchase #2	$157.89	5.784%	$167.0224	$167.02	$167.00	$167.00
Purchase #3	$119.78	6.384%	$127.4268	$127.43	$127.45	$127.40
Purchase #4	$211.79	7.360%	$227.3777	$227.38	$227.40	$227.40
Purchase #5	$99.83	7.724%	$107.5409	$107.54	$107.55	$107.50
Purchase #6	$86.91	9.285%	$94.9796	$94.98	$95.00	$95.00
Purchase #7	$77.33	8.220%	$83.6865	$83.69	$83.70	$83.70
7 purchase totals =	$790.88		$849.5753	$849.58	$849.65	$849.50