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	$125.27	4.469%	$130.8683	$130.87	$130.85	$130.90
Purchase #2	$86.71	10.457%	$95.7773	$95.78	$95.80	$95.80
Purchase #3	$111.60	12.293%	$125.319	$125.32	$125.30	$125.30
Purchase #4	$99.68	10.208%	$109.8553	$109.86	$109.85	$109.90
Purchase #5	$179.73	3.858%	$186.664	$186.66	$186.65	$186.70
Purchase #6	$136.69	8.663%	$148.5315	$148.53	$148.55	$148.50
Purchase #7	$180.82	5.470%	$190.7109	$190.71	$190.70	$190.70
7 purchase totals =	$920.50		$987.7263	$987.73	$987.70	$987.80