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	$193.60	13.347%	$219.4398	$219.44	$219.45	$219.40
Purchase #2	$40.51	13.499%	$45.9784	$45.98	$46.00	$46.00
Purchase #3	$174.70	6.150%	$185.4441	$185.44	$185.45	$185.40
Purchase #4	$89.57	11.852%	$100.1858	$100.19	$100.20	$100.20
Purchase #5	$64.72	5.422%	$68.2291	$68.23	$68.25	$68.20
Purchase #6	$30.44	4.804%	$31.9023	$31.90	$31.90	$31.90
Purchase #7	$136.85	9.721%	$150.1532	$150.15	$150.15	$150.20
7 purchase totals =	$730.39		$801.3327	$801.33	$801.40	$801.30