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	$42.33	5.280%	$44.565	$44.57	$44.55	$44.60
Purchase #2	$166.32	8.112%	$179.8119	$179.81	$179.80	$179.80
Purchase #3	$94.36	9.823%	$103.629	$103.63	$103.65	$103.60
Purchase #4	$97.95	11.809%	$109.5169	$109.52	$109.50	$109.50
Purchase #5	$37.85	11.410%	$42.1687	$42.17	$42.15	$42.20
Purchase #6	$95.29	5.377%	$100.4137	$100.41	$100.40	$100.40
Purchase #7	$177.25	12.615%	$199.6101	$199.61	$199.60	$199.60
7 purchase totals =	$711.35		$779.7153	$779.72	$779.65	$779.70