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	$68.52	13.232%	$77.5866	$77.59	$77.60	$77.60
Purchase #2	$150.55	4.629%	$157.519	$157.52	$157.50	$157.50
Purchase #3	$199.89	4.421%	$208.7271	$208.73	$208.75	$208.70
Purchase #4	$80.47	6.498%	$85.6989	$85.70	$85.70	$85.70
Purchase #5	$221.94	9.730%	$243.5348	$243.53	$243.55	$243.50
Purchase #6	$72.57	7.486%	$78.0026	$78.00	$78.00	$78.00
Purchase #7	$200.27	4.579%	$209.4404	$209.44	$209.45	$209.40
7 purchase totals =	$994.21		$1,060.5094	$1,060.51	$1,060.55	$1,060.40