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	$85.53	8.272%	$92.605	$92.61	$92.60	$92.60
Purchase #2	$200.53	8.831%	$218.2388	$218.24	$218.25	$218.20
Purchase #3	$69.66	3.570%	$72.1469	$72.15	$72.15	$72.10
Purchase #4	$36.69	4.358%	$38.289	$38.29	$38.30	$38.30
Purchase #5	$176.84	8.192%	$191.3267	$191.33	$191.35	$191.30
Purchase #6	$11.42	9.727%	$12.5308	$12.53	$12.55	$12.50
Purchase #7	$39.72	7.303%	$42.6208	$42.62	$42.60	$42.60
7 purchase totals =	$620.39		$667.7580	$667.77	$667.80	$667.60