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	$179.39	6.632%	$191.2871	$191.29	$191.30	$191.30
Purchase #2	$238.74	12.599%	$268.8189	$268.82	$268.80	$268.80
Purchase #3	$136.30	12.281%	$153.039	$153.04	$153.05	$153.00
Purchase #4	$186.25	5.639%	$196.7526	$196.75	$196.75	$196.80
Purchase #5	$179.35	9.376%	$196.1659	$196.17	$196.15	$196.20
Purchase #6	$102.81	4.293%	$107.2236	$107.22	$107.20	$107.20
Purchase #7	$143.78	7.814%	$155.015	$155.02	$155.00	$155.00
7 purchase totals =	$1,166.62		$1,268.3021	$1,268.31	$1,268.25	$1,268.30