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	$200.56	11.664%	$223.9533	$223.95	$223.95	$224.00
Purchase #2	$248.84	12.227%	$279.2657	$279.27	$279.25	$279.30
Purchase #3	$35.87	6.671%	$38.2629	$38.26	$38.25	$38.30
Purchase #4	$167.91	12.384%	$188.704	$188.70	$188.70	$188.70
Purchase #5	$135.86	8.417%	$147.2953	$147.30	$147.30	$147.30
Purchase #6	$44.87	3.534%	$46.4557	$46.46	$46.45	$46.50
Purchase #7	$124.55	10.654%	$137.8196	$137.82	$137.80	$137.80
7 purchase totals =	$958.46		$1,061.7565	$1,061.76	$1,061.70	$1,061.90