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	$65.80	11.631%	$73.4532	$73.45	$73.45	$73.50
Purchase #2	$93.76	11.402%	$104.4505	$104.45	$104.45	$104.50
Purchase #3	$173.75	10.207%	$191.4847	$191.48	$191.50	$191.50
Purchase #4	$56.72	10.564%	$62.7119	$62.71	$62.70	$62.70
Purchase #5	$42.83	11.559%	$47.7807	$47.78	$47.80	$47.80
Purchase #6	$217.29	3.543%	$224.9886	$224.99	$225.00	$225.00
Purchase #7	$221.96	12.838%	$250.4552	$250.46	$250.45	$250.50
7 purchase totals =	$872.11		$955.3248	$955.32	$955.35	$955.50