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	$66.26	7.440%	$71.1897	$71.19	$71.20	$71.20
Purchase #2	$51.40	13.667%	$58.4248	$58.42	$58.40	$58.40
Purchase #3	$93.32	8.139%	$100.9153	$100.92	$100.90	$100.90
Purchase #4	$233.56	6.186%	$248.008	$248.01	$248.00	$248.00
Purchase #5	$156.31	11.394%	$174.12	$174.12	$174.10	$174.10
Purchase #6	$195.33	6.544%	$208.1124	$208.11	$208.10	$208.10
Purchase #7	$140.25	10.632%	$155.1614	$155.16	$155.15	$155.20
7 purchase totals =	$936.43		$1,015.9316	$1,015.93	$1,015.85	$1,015.90