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	$166.68	4.828%	$174.7273	$174.73	$174.75	$174.70
Purchase #2	$77.82	10.374%	$85.893	$85.89	$85.90	$85.90
Purchase #3	$110.50	5.535%	$116.6162	$116.62	$116.60	$116.60
Purchase #4	$116.85	11.775%	$130.6091	$130.61	$130.60	$130.60
Purchase #5	$244.27	7.419%	$262.3924	$262.39	$262.40	$262.40
Purchase #6	$52.94	13.199%	$59.9276	$59.93	$59.95	$59.90
Purchase #7	$140.90	13.269%	$159.596	$159.60	$159.60	$159.60
7 purchase totals =	$909.96		$989.7616	$989.77	$989.80	$989.70