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	$204.67	8.751%	$222.5807	$222.58	$222.60	$222.60
Purchase #2	$186.88	12.250%	$209.7728	$209.77	$209.75	$209.80
Purchase #3	$176.59	13.558%	$200.5321	$200.53	$200.55	$200.50
Purchase #4	$73.52	5.671%	$77.6893	$77.69	$77.70	$77.70
Purchase #5	$42.37	6.533%	$45.138	$45.14	$45.15	$45.10
Purchase #6	$65.51	6.692%	$69.8939	$69.89	$69.90	$69.90
Purchase #7	$178.40	11.449%	$198.825	$198.83	$198.85	$198.80
7 purchase totals =	$927.94		$1,024.4318	$1,024.43	$1,024.50	$1,024.40