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	$223.75	3.538%	$231.6663	$231.67	$231.65	$231.70
Purchase #2	$169.36	10.565%	$187.2529	$187.25	$187.25	$187.30
Purchase #3	$59.84	10.828%	$66.3195	$66.32	$66.30	$66.30
Purchase #4	$72.92	11.200%	$81.087	$81.09	$81.10	$81.10
Purchase #5	$226.52	10.737%	$250.8415	$250.84	$250.85	$250.80
Purchase #6	$98.59	6.279%	$104.7805	$104.78	$104.80	$104.80
Purchase #7	$86.44	9.197%	$94.3899	$94.39	$94.40	$94.40
7 purchase totals =	$937.42		$1,016.3376	$1,016.34	$1,016.35	$1,016.40