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	$159.82	10.614%	$176.7833	$176.78	$176.80	$176.80
Purchase #2	$228.28	9.232%	$249.3548	$249.35	$249.35	$249.40
Purchase #3	$55.53	6.861%	$59.3399	$59.34	$59.35	$59.30
Purchase #4	$37.91	6.326%	$40.3082	$40.31	$40.30	$40.30
Purchase #5	$148.63	10.478%	$164.2035	$164.20	$164.20	$164.20
Purchase #6	$186.28	12.316%	$209.2222	$209.22	$209.20	$209.20
Purchase #7	$110.33	3.189%	$113.8484	$113.85	$113.85	$113.80
7 purchase totals =	$926.78		$1,013.0603	$1,013.05	$1,013.05	$1,013.00