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	$250.94	12.565%	$282.4706	$282.47	$282.45	$282.50
Purchase #2	$16.76	11.354%	$18.6629	$18.66	$18.65	$18.70
Purchase #3	$158.25	10.357%	$174.64	$174.64	$174.65	$174.60
Purchase #4	$76.91	11.235%	$85.5508	$85.55	$85.55	$85.60
Purchase #5	$102.55	6.596%	$109.3142	$109.31	$109.30	$109.30
Purchase #6	$206.75	7.837%	$222.953	$222.95	$222.95	$223.00
Purchase #7	$118.64	3.711%	$123.0427	$123.04	$123.05	$123.00
7 purchase totals =	$930.80		$1,016.6342	$1,016.62	$1,016.60	$1,016.70