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	$151.47	10.415%	$167.2456	$167.25	$167.25	$167.20
Purchase #2	$45.69	7.720%	$49.2173	$49.22	$49.20	$49.20
Purchase #3	$190.55	6.215%	$202.3927	$202.39	$202.40	$202.40
Purchase #4	$82.59	3.618%	$85.5781	$85.58	$85.60	$85.60
Purchase #5	$45.31	9.144%	$49.4531	$49.45	$49.45	$49.50
Purchase #6	$246.94	13.582%	$280.4794	$280.48	$280.50	$280.50
Purchase #7	$219.73	5.553%	$231.9316	$231.93	$231.95	$231.90
7 purchase totals =	$982.28		$1,066.2978	$1,066.30	$1,066.35	$1,066.30