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	$84.27	4.681%	$88.2147	$88.21	$88.20	$88.20
Purchase #2	$118.25	7.670%	$127.3198	$127.32	$127.30	$127.30
Purchase #3	$149.61	12.622%	$168.4938	$168.49	$168.50	$168.50
Purchase #4	$106.78	13.427%	$121.1174	$121.12	$121.10	$121.10
Purchase #5	$191.65	12.703%	$215.9953	$216.00	$216.00	$216.00
Purchase #6	$138.51	4.401%	$144.6058	$144.61	$144.60	$144.60
Purchase #7	$137.30	9.653%	$150.5536	$150.55	$150.55	$150.60
7 purchase totals =	$926.37		$1,016.3004	$1,016.30	$1,016.25	$1,016.30