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	$175.38	4.122%	$182.6092	$182.61	$182.60	$182.60
Purchase #2	$194.52	7.411%	$208.9359	$208.94	$208.95	$208.90
Purchase #3	$72.64	7.796%	$78.303	$78.30	$78.30	$78.30
Purchase #4	$29.40	6.309%	$31.2548	$31.25	$31.25	$31.30
Purchase #5	$33.55	9.686%	$36.7997	$36.80	$36.80	$36.80
Purchase #6	$72.91	9.855%	$80.0953	$80.10	$80.10	$80.10
Purchase #7	$42.38	13.717%	$48.1933	$48.19	$48.20	$48.20
7 purchase totals =	$620.78		$666.1912	$666.19	$666.20	$666.20