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	$159.70	5.473%	$168.4404	$168.44	$168.45	$168.40
Purchase #2	$188.60	13.252%	$213.5933	$213.59	$213.60	$213.60
Purchase #3	$16.31	11.208%	$18.138	$18.14	$18.15	$18.10
Purchase #4	$109.50	6.488%	$116.6044	$116.60	$116.60	$116.60
Purchase #5	$104.87	4.330%	$109.4109	$109.41	$109.40	$109.40
Purchase #6	$5.46	10.198%	$6.0168	$6.02	$6.00	$6.00
Purchase #7	$191.51	11.394%	$213.3306	$213.33	$213.35	$213.30
7 purchase totals =	$775.95		$845.5344	$845.53	$845.55	$845.40