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	$41.98	4.214%	$43.749	$43.75	$43.75	$43.70
Purchase #2	$110.42	13.417%	$125.2351	$125.24	$125.25	$125.20
Purchase #3	$156.60	12.684%	$176.4631	$176.46	$176.45	$176.50
Purchase #4	$82.94	10.330%	$91.5077	$91.51	$91.50	$91.50
Purchase #5	$68.31	5.595%	$72.1319	$72.13	$72.15	$72.10
Purchase #6	$187.69	11.374%	$209.0379	$209.04	$209.05	$209.00
Purchase #7	$100.30	9.444%	$109.7723	$109.77	$109.75	$109.80
7 purchase totals =	$748.24		$827.8970	$827.90	$827.90	$827.80