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	$62.57	5.841%	$66.2247	$66.22	$66.20	$66.20
Purchase #2	$48.67	10.598%	$53.828	$53.83	$53.85	$53.80
Purchase #3	$99.33	6.431%	$105.7179	$105.72	$105.70	$105.70
Purchase #4	$24.54	4.360%	$25.6099	$25.61	$25.60	$25.60
Purchase #5	$198.74	6.134%	$210.9307	$210.93	$210.95	$210.90
Purchase #6	$214.39	10.792%	$237.527	$237.53	$237.55	$237.50
Purchase #7	$93.35	10.235%	$102.9044	$102.90	$102.90	$102.90
7 purchase totals =	$741.59		$802.7426	$802.74	$802.75	$802.60