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	$151.95	6.781%	$162.2537	$162.25	$162.25	$162.30
Purchase #2	$154.83	6.151%	$164.3536	$164.35	$164.35	$164.40
Purchase #3	$179.30	8.729%	$194.9511	$194.95	$194.95	$195.00
Purchase #4	$109.73	13.672%	$124.7323	$124.73	$124.75	$124.70
Purchase #5	$40.57	3.805%	$42.1137	$42.11	$42.10	$42.10
Purchase #6	$33.76	3.139%	$34.8197	$34.82	$34.80	$34.80
Purchase #7	$244.71	4.524%	$255.7807	$255.78	$255.80	$255.80
7 purchase totals =	$914.85		$979.0048	$978.99	$979.00	$979.10