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	$246.72	7.789%	$265.937	$265.94	$265.95	$265.90
Purchase #2	$33.54	10.345%	$37.0097	$37.01	$37.00	$37.00
Purchase #3	$69.91	12.247%	$78.4719	$78.47	$78.45	$78.50
Purchase #4	$51.43	7.815%	$55.4493	$55.45	$55.45	$55.40
Purchase #5	$85.92	11.505%	$95.8051	$95.81	$95.80	$95.80
Purchase #6	$110.76	4.321%	$115.5459	$115.55	$115.55	$115.50
Purchase #7	$38.77	8.392%	$42.0236	$42.02	$42.00	$42.00
7 purchase totals =	$637.05		$690.2425	$690.25	$690.20	$690.10