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	$154.44	13.834%	$175.8052	$175.81	$175.80	$175.80
Purchase #2	$37.38	5.344%	$39.3776	$39.38	$39.40	$39.40
Purchase #3	$96.63	5.567%	$102.0094	$102.01	$102.00	$102.00
Purchase #4	$67.29	8.616%	$73.0877	$73.09	$73.10	$73.10
Purchase #5	$191.36	4.806%	$200.5568	$200.56	$200.55	$200.60
Purchase #6	$158.77	12.645%	$178.8465	$178.85	$178.85	$178.80
Purchase #7	$53.90	4.789%	$56.4813	$56.48	$56.50	$56.50
7 purchase totals =	$759.77		$826.1645	$826.18	$826.20	$826.20