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	$200.36	11.167%	$222.7342	$222.73	$222.75	$222.70
Purchase #2	$167.91	3.342%	$173.5216	$173.52	$173.50	$173.50
Purchase #3	$6.65	4.467%	$6.9471	$6.95	$6.95	$6.90
Purchase #4	$72.79	13.207%	$82.4034	$82.40	$82.40	$82.40
Purchase #5	$225.88	10.830%	$250.3428	$250.34	$250.35	$250.30
Purchase #6	$212.92	12.574%	$239.6926	$239.69	$239.70	$239.70
Purchase #7	$55.32	6.539%	$58.9374	$58.94	$58.95	$58.90
7 purchase totals =	$941.83		$1,034.5791	$1,034.57	$1,034.60	$1,034.40