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	$154.73	4.314%	$161.4051	$161.41	$161.40	$161.40
Purchase #2	$153.25	10.233%	$168.9321	$168.93	$168.95	$168.90
Purchase #3	$233.65	8.658%	$253.8794	$253.88	$253.90	$253.90
Purchase #4	$141.58	3.460%	$146.4787	$146.48	$146.50	$146.50
Purchase #5	$29.41	12.612%	$33.1192	$33.12	$33.10	$33.10
Purchase #6	$84.31	12.656%	$94.9803	$94.98	$95.00	$95.00
Purchase #7	$217.86	11.109%	$242.0621	$242.06	$242.05	$242.10
7 purchase totals =	$1,014.79		$1,100.8569	$1,100.86	$1,100.90	$1,100.90