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	$136.83	11.271%	$152.2521	$152.25	$152.25	$152.30
Purchase #2	$66.30	10.360%	$73.1687	$73.17	$73.15	$73.20
Purchase #3	$206.86	10.380%	$228.3321	$228.33	$228.35	$228.30
Purchase #4	$120.64	6.614%	$128.6191	$128.62	$128.60	$128.60
Purchase #5	$231.57	12.216%	$259.8586	$259.86	$259.85	$259.90
Purchase #6	$167.85	5.659%	$177.3486	$177.35	$177.35	$177.30
Purchase #7	$84.90	7.123%	$90.9474	$90.95	$90.95	$90.90
7 purchase totals =	$1,014.95		$1,110.5266	$1,110.53	$1,110.50	$1,110.50