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	$85.78	4.558%	$89.6899	$89.69	$89.70	$89.70
Purchase #2	$24.44	3.658%	$25.334	$25.33	$25.35	$25.30
Purchase #3	$19.59	8.131%	$21.1829	$21.18	$21.20	$21.20
Purchase #4	$13.46	13.694%	$15.3032	$15.30	$15.30	$15.30
Purchase #5	$178.39	9.139%	$194.6931	$194.69	$194.70	$194.70
Purchase #6	$59.96	3.366%	$61.9783	$61.98	$62.00	$62.00
Purchase #7	$102.44	13.488%	$116.2571	$116.26	$116.25	$116.30
7 purchase totals =	$484.06		$524.4385	$524.43	$524.50	$524.50