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	$167.45	13.487%	$190.034	$190.03	$190.05	$190.00
Purchase #2	$163.57	9.638%	$179.3349	$179.33	$179.35	$179.30
Purchase #3	$48.93	13.359%	$55.4666	$55.47	$55.45	$55.50
Purchase #4	$90.76	12.272%	$101.8981	$101.90	$101.90	$101.90
Purchase #5	$71.53	12.633%	$80.5664	$80.57	$80.55	$80.60
Purchase #6	$109.70	7.813%	$118.2709	$118.27	$118.25	$118.30
Purchase #7	$140.53	11.424%	$156.5841	$156.58	$156.60	$156.60
7 purchase totals =	$792.47		$882.1550	$882.15	$882.15	$882.20