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	$191.29	4.852%	$200.5714	$200.57	$200.55	$200.60
Purchase #2	$27.64	13.399%	$31.3435	$31.34	$31.35	$31.30
Purchase #3	$56.80	4.459%	$59.3327	$59.33	$59.35	$59.30
Purchase #4	$100.28	13.123%	$113.4397	$113.44	$113.45	$113.40
Purchase #5	$70.68	9.150%	$77.1472	$77.15	$77.15	$77.10
Purchase #6	$24.66	11.755%	$27.5588	$27.56	$27.55	$27.60
Purchase #7	$20.64	13.773%	$23.4827	$23.48	$23.50	$23.50
7 purchase totals =	$491.99		$532.8760	$532.87	$532.90	$532.80