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	$77.98	5.670%	$82.4015	$82.40	$82.40	$82.40
Purchase #2	$151.66	11.264%	$168.743	$168.74	$168.75	$168.70
Purchase #3	$116.57	7.769%	$125.6263	$125.63	$125.65	$125.60
Purchase #4	$41.38	9.850%	$45.4559	$45.46	$45.45	$45.50
Purchase #5	$85.39	5.264%	$89.8849	$89.88	$89.90	$89.90
Purchase #6	$176.75	7.686%	$190.335	$190.34	$190.35	$190.30
Purchase #7	$241.95	10.148%	$266.5031	$266.50	$266.50	$266.50
7 purchase totals =	$891.68		$968.9497	$968.95	$969.00	$968.90