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	$98.31	5.630%	$103.8449	$103.84	$103.85	$103.80
Purchase #2	$72.80	10.698%	$80.5881	$80.59	$80.60	$80.60
Purchase #3	$184.46	10.855%	$204.4831	$204.48	$204.50	$204.50
Purchase #4	$199.54	13.415%	$226.3083	$226.31	$226.30	$226.30
Purchase #5	$211.93	11.484%	$236.268	$236.27	$236.25	$236.30
Purchase #6	$82.72	3.126%	$85.3058	$85.31	$85.30	$85.30
Purchase #7	$53.41	7.617%	$57.4782	$57.48	$57.50	$57.50
7 purchase totals =	$903.17		$994.2764	$994.28	$994.30	$994.30