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	$247.39	9.107%	$269.9198	$269.92	$269.90	$269.90
Purchase #2	$131.56	4.627%	$137.6473	$137.65	$137.65	$137.60
Purchase #3	$58.96	9.772%	$64.7216	$64.72	$64.70	$64.70
Purchase #4	$28.27	4.294%	$29.4839	$29.48	$29.50	$29.50
Purchase #5	$33.60	5.636%	$35.4937	$35.49	$35.50	$35.50
Purchase #6	$135.50	7.707%	$145.943	$145.94	$145.95	$145.90
Purchase #7	$118.58	10.862%	$131.4602	$131.46	$131.45	$131.50
7 purchase totals =	$753.86		$814.6695	$814.66	$814.65	$814.60