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	$179.92	13.642%	$204.4647	$204.46	$204.45	$204.50
Purchase #2	$41.86	11.607%	$46.7187	$46.72	$46.70	$46.70
Purchase #3	$129.25	10.319%	$142.5873	$142.59	$142.60	$142.60
Purchase #4	$174.41	9.336%	$190.6929	$190.69	$190.70	$190.70
Purchase #5	$203.97	7.799%	$219.8776	$219.88	$219.90	$219.90
Purchase #6	$198.66	11.780%	$222.0621	$222.06	$222.05	$222.10
Purchase #7	$79.86	9.493%	$87.4411	$87.44	$87.45	$87.40
7 purchase totals =	$1,007.93		$1,113.8444	$1,113.84	$1,113.85	$1,113.90