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	$30.56	8.679%	$33.2123	$33.21	$33.20	$33.20
Purchase #2	$109.38	8.824%	$119.0317	$119.03	$119.05	$119.00
Purchase #3	$68.47	4.649%	$71.6532	$71.65	$71.65	$71.70
Purchase #4	$78.93	8.105%	$85.3273	$85.33	$85.35	$85.30
Purchase #5	$150.59	9.455%	$164.8283	$164.83	$164.85	$164.80
Purchase #6	$210.28	5.801%	$222.4783	$222.48	$222.50	$222.50
Purchase #7	$212.30	4.367%	$221.5711	$221.57	$221.55	$221.60
7 purchase totals =	$860.51		$918.1022	$918.10	$918.15	$918.10