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	$33.29	10.539%	$36.7984	$36.80	$36.80	$36.80
Purchase #2	$55.96	5.560%	$59.0714	$59.07	$59.05	$59.10
Purchase #3	$229.72	4.862%	$240.889	$240.89	$240.90	$240.90
Purchase #4	$240.89	8.585%	$261.5704	$261.57	$261.55	$261.60
Purchase #5	$87.76	11.407%	$97.7708	$97.77	$97.75	$97.80
Purchase #6	$232.58	10.712%	$257.494	$257.49	$257.50	$257.50
Purchase #7	$85.48	4.238%	$89.1026	$89.10	$89.10	$89.10
7 purchase totals =	$965.68		$1,042.6966	$1,042.69	$1,042.65	$1,042.80