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	$33.63	5.211%	$35.3825	$35.38	$35.40	$35.40
Purchase #2	$137.89	7.316%	$147.978	$147.98	$148.00	$148.00
Purchase #3	$189.61	8.371%	$205.4823	$205.48	$205.50	$205.50
Purchase #4	$64.57	3.374%	$66.7486	$66.75	$66.75	$66.70
Purchase #5	$208.58	7.125%	$223.4413	$223.44	$223.45	$223.40
Purchase #6	$189.83	13.406%	$215.2786	$215.28	$215.30	$215.30
Purchase #7	$178.46	10.120%	$196.5202	$196.52	$196.50	$196.50
7 purchase totals =	$1,002.57		$1,090.8315	$1,090.83	$1,090.90	$1,090.80