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	$60.83	7.707%	$65.5182	$65.52	$65.50	$65.50
Purchase #2	$73.90	7.625%	$79.5349	$79.53	$79.55	$79.50
Purchase #3	$86.43	11.303%	$96.1992	$96.20	$96.20	$96.20
Purchase #4	$154.55	4.824%	$162.0055	$162.01	$162.00	$162.00
Purchase #5	$27.50	3.827%	$28.5524	$28.55	$28.55	$28.60
Purchase #6	$42.45	6.319%	$45.1324	$45.13	$45.15	$45.10
Purchase #7	$33.85	11.729%	$37.8203	$37.82	$37.80	$37.80
7 purchase totals =	$479.51		$514.7629	$514.76	$514.75	$514.70