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	$138.79	4.741%	$145.37	$145.37	$145.35	$145.40
Purchase #2	$29.44	6.860%	$31.4596	$31.46	$31.45	$31.50
Purchase #3	$145.62	3.564%	$150.8099	$150.81	$150.80	$150.80
Purchase #4	$156.46	6.712%	$166.9616	$166.96	$166.95	$167.00
Purchase #5	$187.42	7.393%	$201.276	$201.28	$201.30	$201.30
Purchase #6	$97.99	13.717%	$111.4313	$111.43	$111.45	$111.40
Purchase #7	$226.83	7.252%	$243.2797	$243.28	$243.30	$243.30
7 purchase totals =	$982.55		$1,050.5881	$1,050.59	$1,050.60	$1,050.70