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	$241.45	13.238%	$273.4132	$273.41	$273.40	$273.40
Purchase #2	$37.25	4.248%	$38.8324	$38.83	$38.85	$38.80
Purchase #3	$81.33	6.829%	$86.884	$86.88	$86.90	$86.90
Purchase #4	$194.62	7.819%	$209.8373	$209.84	$209.85	$209.80
Purchase #5	$198.57	8.579%	$215.6053	$215.61	$215.60	$215.60
Purchase #6	$199.85	8.511%	$216.8592	$216.86	$216.85	$216.90
Purchase #7	$119.47	6.837%	$127.6382	$127.64	$127.65	$127.60
7 purchase totals =	$1,072.54		$1,169.0696	$1,169.07	$1,169.10	$1,169.00