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	$32.87	3.686%	$34.0816	$34.08	$34.10	$34.10
Purchase #2	$40.33	4.512%	$42.1497	$42.15	$42.15	$42.10
Purchase #3	$84.71	12.417%	$95.2284	$95.23	$95.25	$95.20
Purchase #4	$41.41	13.828%	$47.1362	$47.14	$47.15	$47.10
Purchase #5	$44.47	5.247%	$46.8033	$46.80	$46.80	$46.80
Purchase #6	$228.89	6.387%	$243.5092	$243.51	$243.50	$243.50
Purchase #7	$94.78	4.172%	$98.7342	$98.73	$98.75	$98.70
7 purchase totals =	$567.46		$607.6426	$607.64	$607.70	$607.50