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	$173.96	4.715%	$182.1622	$182.16	$182.15	$182.20
Purchase #2	$135.94	10.517%	$150.2368	$150.24	$150.25	$150.20
Purchase #3	$121.80	8.286%	$131.8923	$131.89	$131.90	$131.90
Purchase #4	$109.61	7.588%	$117.9272	$117.93	$117.95	$117.90
Purchase #5	$155.31	12.253%	$174.3401	$174.34	$174.35	$174.30
Purchase #6	$208.55	6.658%	$222.4353	$222.44	$222.45	$222.40
Purchase #7	$78.26	6.332%	$83.2154	$83.22	$83.20	$83.20
7 purchase totals =	$983.43		$1,062.2093	$1,062.22	$1,062.25	$1,062.10