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	$111.42	6.635%	$118.8127	$118.81	$118.80	$118.80
Purchase #2	$42.48	3.758%	$44.0764	$44.08	$44.10	$44.10
Purchase #3	$126.34	3.212%	$130.398	$130.40	$130.40	$130.40
Purchase #4	$187.26	4.769%	$196.1904	$196.19	$196.20	$196.20
Purchase #5	$190.54	5.105%	$200.2671	$200.27	$200.25	$200.30
Purchase #6	$78.86	4.416%	$82.3425	$82.34	$82.35	$82.30
Purchase #7	$248.58	11.868%	$278.0815	$278.08	$278.10	$278.10
7 purchase totals =	$985.48		$1,050.1686	$1,050.17	$1,050.20	$1,050.20