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	$193.79	6.649%	$206.6751	$206.68	$206.70	$206.70
Purchase #2	$79.47	12.839%	$89.6732	$89.67	$89.65	$89.70
Purchase #3	$210.93	5.473%	$222.4742	$222.47	$222.45	$222.50
Purchase #4	$89.73	13.367%	$101.7242	$101.72	$101.70	$101.70
Purchase #5	$133.86	4.872%	$140.3817	$140.38	$140.40	$140.40
Purchase #6	$54.69	5.785%	$57.8538	$57.85	$57.85	$57.90
Purchase #7	$148.91	6.518%	$158.616	$158.62	$158.60	$158.60
7 purchase totals =	$911.38		$977.3982	$977.39	$977.35	$977.50