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	$123.39	6.243%	$131.0932	$131.09	$131.10	$131.10
Purchase #2	$97.50	6.626%	$103.9604	$103.96	$103.95	$104.00
Purchase #3	$115.46	3.265%	$119.2298	$119.23	$119.25	$119.20
Purchase #4	$169.63	12.862%	$191.4478	$191.45	$191.45	$191.40
Purchase #5	$217.82	12.717%	$245.5202	$245.52	$245.50	$245.50
Purchase #6	$146.47	4.424%	$152.9498	$152.95	$152.95	$152.90
Purchase #7	$153.48	10.681%	$169.8732	$169.87	$169.85	$169.90
7 purchase totals =	$1,023.75		$1,114.0744	$1,114.07	$1,114.05	$1,114.00