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	$130.96	12.669%	$147.5513	$147.55	$147.55	$147.60
Purchase #2	$78.40	6.568%	$83.5493	$83.55	$83.55	$83.50
Purchase #3	$88.33	9.388%	$96.6224	$96.62	$96.60	$96.60
Purchase #4	$59.33	8.540%	$64.3968	$64.40	$64.40	$64.40
Purchase #5	$101.53	3.477%	$105.0602	$105.06	$105.05	$105.10
Purchase #6	$92.37	7.574%	$99.3661	$99.37	$99.35	$99.40
Purchase #7	$28.97	4.822%	$30.3669	$30.37	$30.35	$30.40
7 purchase totals =	$579.89		$626.9130	$626.92	$626.85	$627.00