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	$145.54	10.368%	$160.6296	$160.63	$160.65	$160.60
Purchase #2	$135.84	4.734%	$142.2707	$142.27	$142.25	$142.30
Purchase #3	$18.96	6.109%	$20.1183	$20.12	$20.10	$20.10
Purchase #4	$189.76	8.572%	$206.0262	$206.03	$206.05	$206.00
Purchase #5	$32.25	3.426%	$33.3549	$33.35	$33.35	$33.40
Purchase #6	$14.50	3.505%	$15.0082	$15.01	$15.00	$15.00
Purchase #7	$89.28	12.587%	$100.5177	$100.52	$100.50	$100.50
7 purchase totals =	$626.13		$677.9256	$677.93	$677.90	$677.90