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	$79.95	6.766%	$85.3594	$85.36	$85.35	$85.40
Purchase #2	$54.26	5.256%	$57.1119	$57.11	$57.10	$57.10
Purchase #3	$109.62	3.743%	$113.7231	$113.72	$113.70	$113.70
Purchase #4	$119.38	10.148%	$131.4947	$131.49	$131.50	$131.50
Purchase #5	$180.36	3.166%	$186.0702	$186.07	$186.05	$186.10
Purchase #6	$168.39	13.361%	$190.8886	$190.89	$190.90	$190.90
Purchase #7	$35.82	13.713%	$40.732	$40.73	$40.75	$40.70
7 purchase totals =	$747.78		$805.3799	$805.37	$805.35	$805.40