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	$106.39	5.595%	$112.3425	$112.34	$112.35	$112.30
Purchase #2	$60.52	11.750%	$67.6311	$67.63	$67.65	$67.60
Purchase #3	$88.64	12.596%	$99.8051	$99.81	$99.80	$99.80
Purchase #4	$28.35	10.382%	$31.2933	$31.29	$31.30	$31.30
Purchase #5	$242.64	11.462%	$270.4514	$270.45	$270.45	$270.50
Purchase #6	$161.54	11.740%	$180.5048	$180.50	$180.50	$180.50
Purchase #7	$128.94	8.667%	$140.1152	$140.12	$140.10	$140.10
7 purchase totals =	$817.02		$902.1434	$902.14	$902.15	$902.10