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	$136.78	10.425%	$151.0393	$151.04	$151.05	$151.00
Purchase #2	$122.47	10.656%	$135.5204	$135.52	$135.50	$135.50
Purchase #3	$7.47	5.134%	$7.8535	$7.85	$7.85	$7.90
Purchase #4	$134.79	6.325%	$143.3155	$143.32	$143.30	$143.30
Purchase #5	$162.27	7.247%	$174.0297	$174.03	$174.05	$174.00
Purchase #6	$241.96	11.801%	$270.5137	$270.51	$270.50	$270.50
Purchase #7	$105.43	3.437%	$109.0536	$109.05	$109.05	$109.10
7 purchase totals =	$911.17		$991.3257	$991.32	$991.30	$991.30