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	$63.76	13.360%	$72.2783	$72.28	$72.30	$72.30
Purchase #2	$9.78	8.331%	$10.5948	$10.59	$10.60	$10.60
Purchase #3	$171.50	9.586%	$187.94	$187.94	$187.95	$187.90
Purchase #4	$250.86	6.806%	$267.9335	$267.93	$267.95	$267.90
Purchase #5	$175.26	3.613%	$181.5921	$181.59	$181.60	$181.60
Purchase #6	$82.36	9.872%	$90.4906	$90.49	$90.50	$90.50
Purchase #7	$213.78	3.821%	$221.9485	$221.95	$221.95	$221.90
7 purchase totals =	$967.30		$1,032.7778	$1,032.77	$1,032.85	$1,032.70