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	$11.60	4.107%	$12.0764	$12.08	$12.10	$12.10
Purchase #2	$109.85	4.728%	$115.0437	$115.04	$115.05	$115.00
Purchase #3	$51.70	10.618%	$57.1895	$57.19	$57.20	$57.20
Purchase #4	$90.68	13.814%	$103.2065	$103.21	$103.20	$103.20
Purchase #5	$69.71	12.623%	$78.5095	$78.51	$78.50	$78.50
Purchase #6	$85.96	9.417%	$94.0549	$94.05	$94.05	$94.10
Purchase #7	$88.25	13.504%	$100.1673	$100.17	$100.15	$100.20
7 purchase totals =	$507.75		$560.2478	$560.25	$560.25	$560.30