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	$227.31	5.612%	$240.0666	$240.07	$240.05	$240.10
Purchase #2	$151.94	4.279%	$158.4415	$158.44	$158.45	$158.40
Purchase #3	$73.50	12.786%	$82.8977	$82.90	$82.90	$82.90
Purchase #4	$155.63	12.568%	$175.1896	$175.19	$175.20	$175.20
Purchase #5	$140.34	7.143%	$150.3645	$150.36	$150.35	$150.40
Purchase #6	$219.57	11.359%	$244.511	$244.51	$244.50	$244.50
Purchase #7	$143.25	5.320%	$150.8709	$150.87	$150.85	$150.90
7 purchase totals =	$1,111.54		$1,202.3418	$1,202.34	$1,202.30	$1,202.40