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	$191.74	7.154%	$205.4571	$205.46	$205.45	$205.50
Purchase #2	$167.96	10.667%	$185.8763	$185.88	$185.90	$185.90
Purchase #3	$108.88	6.472%	$115.9267	$115.93	$115.95	$115.90
Purchase #4	$41.36	8.741%	$44.9753	$44.98	$45.00	$45.00
Purchase #5	$18.97	5.575%	$20.0276	$20.03	$20.05	$20.00
Purchase #6	$128.70	10.456%	$142.1569	$142.16	$142.15	$142.20
Purchase #7	$131.69	12.466%	$148.1065	$148.11	$148.10	$148.10
7 purchase totals =	$789.30		$862.5264	$862.55	$862.60	$862.60