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	$98.89	12.409%	$111.1613	$111.16	$111.15	$111.20
Purchase #2	$215.40	7.491%	$231.5356	$231.54	$231.55	$231.50
Purchase #3	$163.58	6.871%	$174.8196	$174.82	$174.80	$174.80
Purchase #4	$148.91	12.511%	$167.5401	$167.54	$167.55	$167.50
Purchase #5	$160.91	11.534%	$179.4694	$179.47	$179.45	$179.50
Purchase #6	$10.86	6.546%	$11.5709	$11.57	$11.55	$11.60
Purchase #7	$67.33	7.632%	$72.4686	$72.47	$72.45	$72.50
7 purchase totals =	$865.88		$948.5655	$948.57	$948.50	$948.60