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	$163.38	3.298%	$168.7683	$168.77	$168.75	$168.80
Purchase #2	$57.89	11.449%	$64.5178	$64.52	$64.50	$64.50
Purchase #3	$187.86	5.435%	$198.0702	$198.07	$198.05	$198.10
Purchase #4	$118.62	6.533%	$126.3694	$126.37	$126.35	$126.40
Purchase #5	$165.85	3.584%	$171.7941	$171.79	$171.80	$171.80
Purchase #6	$240.74	6.155%	$255.5575	$255.56	$255.55	$255.60
Purchase #7	$78.78	7.275%	$84.5112	$84.51	$84.50	$84.50
7 purchase totals =	$1,013.12		$1,069.5885	$1,069.59	$1,069.50	$1,069.70