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	$162.48	5.514%	$171.4391	$171.44	$171.45	$171.40
Purchase #2	$134.80	8.785%	$146.6422	$146.64	$146.65	$146.60
Purchase #3	$61.55	7.714%	$66.298	$66.30	$66.30	$66.30
Purchase #4	$141.48	8.293%	$153.2129	$153.21	$153.20	$153.20
Purchase #5	$129.82	3.472%	$134.3274	$134.33	$134.35	$134.30
Purchase #6	$224.99	6.172%	$238.8764	$238.88	$238.90	$238.90
Purchase #7	$85.98	7.703%	$92.603	$92.60	$92.60	$92.60
7 purchase totals =	$941.10		$1,003.3990	$1,003.40	$1,003.45	$1,003.30