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	$80.59	6.747%	$86.0274	$86.03	$86.05	$86.00
Purchase #2	$19.48	7.227%	$20.8878	$20.89	$20.90	$20.90
Purchase #3	$117.48	10.252%	$129.524	$129.52	$129.50	$129.50
Purchase #4	$117.56	13.747%	$133.721	$133.72	$133.70	$133.70
Purchase #5	$171.61	13.816%	$195.3196	$195.32	$195.30	$195.30
Purchase #6	$9.88	3.542%	$10.2299	$10.23	$10.25	$10.20
Purchase #7	$196.81	13.650%	$223.6746	$223.67	$223.65	$223.70
7 purchase totals =	$713.41		$799.3843	$799.38	$799.35	$799.30