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	$98.78	7.707%	$106.393	$106.39	$106.40	$106.40
Purchase #2	$153.43	13.709%	$174.4637	$174.46	$174.45	$174.50
Purchase #3	$222.85	9.267%	$243.5015	$243.50	$243.50	$243.50
Purchase #4	$81.39	13.673%	$92.5185	$92.52	$92.50	$92.50
Purchase #5	$81.68	5.874%	$86.4779	$86.48	$86.50	$86.50
Purchase #6	$32.62	3.579%	$33.7875	$33.79	$33.80	$33.80
Purchase #7	$38.43	10.787%	$42.5754	$42.58	$42.60	$42.60
7 purchase totals =	$709.18		$779.7175	$779.72	$779.75	$779.80