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	$224.87	11.541%	$250.8222	$250.82	$250.80	$250.80
Purchase #2	$86.92	10.571%	$96.1083	$96.11	$96.10	$96.10
Purchase #3	$191.49	9.443%	$209.5724	$209.57	$209.55	$209.60
Purchase #4	$113.72	12.813%	$128.2909	$128.29	$128.30	$128.30
Purchase #5	$179.38	11.246%	$199.5531	$199.55	$199.55	$199.60
Purchase #6	$132.83	7.197%	$142.3898	$142.39	$142.40	$142.40
Purchase #7	$178.53	12.273%	$200.441	$200.44	$200.45	$200.40
7 purchase totals =	$1,107.74		$1,227.1777	$1,227.17	$1,227.15	$1,227.20