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	$42.89	3.265%	$44.2904	$44.29	$44.30	$44.30
Purchase #2	$165.48	3.350%	$171.0236	$171.02	$171.00	$171.00
Purchase #3	$94.78	4.256%	$98.8138	$98.81	$98.80	$98.80
Purchase #4	$243.50	7.389%	$261.4922	$261.49	$261.50	$261.50
Purchase #5	$35.45	13.676%	$40.2981	$40.30	$40.30	$40.30
Purchase #6	$26.92	12.834%	$30.3749	$30.37	$30.35	$30.40
Purchase #7	$165.48	13.649%	$188.0664	$188.07	$188.05	$188.10
7 purchase totals =	$774.50		$834.3594	$834.35	$834.30	$834.40