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	$189.43	4.446%	$197.8521	$197.85	$197.85	$197.90
Purchase #2	$117.70	10.448%	$129.9973	$130.00	$130.00	$130.00
Purchase #3	$179.39	3.456%	$185.5897	$185.59	$185.60	$185.60
Purchase #4	$130.85	9.224%	$142.9196	$142.92	$142.90	$142.90
Purchase #5	$115.52	9.420%	$126.402	$126.40	$126.40	$126.40
Purchase #6	$189.38	10.857%	$209.941	$209.94	$209.95	$209.90
Purchase #7	$67.45	7.164%	$72.2821	$72.28	$72.30	$72.30
7 purchase totals =	$989.72		$1,064.9838	$1,064.98	$1,065.00	$1,065.00