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	$226.44	10.170%	$249.4689	$249.47	$249.45	$249.50
Purchase #2	$58.46	8.657%	$63.5209	$63.52	$63.50	$63.50
Purchase #3	$131.27	8.873%	$142.9176	$142.92	$142.90	$142.90
Purchase #4	$182.85	7.496%	$196.5564	$196.56	$196.55	$196.60
Purchase #5	$130.83	13.334%	$148.2749	$148.27	$148.25	$148.30
Purchase #6	$6.57	5.694%	$6.9441	$6.94	$6.95	$6.90
Purchase #7	$239.87	11.137%	$266.5843	$266.58	$266.60	$266.60
7 purchase totals =	$976.29		$1,074.2671	$1,074.26	$1,074.20	$1,074.30