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	$131.62	11.298%	$146.4904	$146.49	$146.50	$146.50
Purchase #2	$164.68	12.315%	$184.9603	$184.96	$184.95	$185.00
Purchase #3	$179.85	3.407%	$185.9775	$185.98	$186.00	$186.00
Purchase #4	$97.72	12.281%	$109.721	$109.72	$109.70	$109.70
Purchase #5	$95.95	9.247%	$104.8225	$104.82	$104.80	$104.80
Purchase #6	$12.31	12.332%	$13.8281	$13.83	$13.85	$13.80
Purchase #7	$244.37	8.298%	$264.6478	$264.65	$264.65	$264.60
7 purchase totals =	$926.50		$1,010.4476	$1,010.45	$1,010.45	$1,010.40