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	$96.49	4.681%	$101.0067	$101.01	$101.00	$101.00
Purchase #2	$31.80	4.641%	$33.2758	$33.28	$33.30	$33.30
Purchase #3	$99.99	9.529%	$109.518	$109.52	$109.50	$109.50
Purchase #4	$145.54	8.520%	$157.94	$157.94	$157.95	$157.90
Purchase #5	$145.95	7.212%	$156.4759	$156.48	$156.50	$156.50
Purchase #6	$84.85	5.271%	$89.3224	$89.32	$89.30	$89.30
Purchase #7	$223.38	11.676%	$249.4618	$249.46	$249.45	$249.50
7 purchase totals =	$828.00		$897.0006	$897.01	$897.00	$897.00