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	$73.52	12.471%	$82.6887	$82.69	$82.70	$82.70
Purchase #2	$237.59	13.314%	$269.2227	$269.22	$269.20	$269.20
Purchase #3	$42.30	11.797%	$47.2901	$47.29	$47.30	$47.30
Purchase #4	$120.50	4.801%	$126.2852	$126.29	$126.30	$126.30
Purchase #5	$210.89	10.423%	$232.8711	$232.87	$232.85	$232.90
Purchase #6	$207.62	4.750%	$217.482	$217.48	$217.50	$217.50
Purchase #7	$197.44	11.620%	$220.3825	$220.38	$220.40	$220.40
7 purchase totals =	$1,089.86		$1,196.2223	$1,196.22	$1,196.25	$1,196.30