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	$130.28	7.802%	$140.4444	$140.44	$140.45	$140.40
Purchase #2	$150.85	11.537%	$168.2536	$168.25	$168.25	$168.30
Purchase #3	$12.56	10.678%	$13.9012	$13.90	$13.90	$13.90
Purchase #4	$22.27	5.637%	$23.5254	$23.53	$23.55	$23.50
Purchase #5	$189.45	3.836%	$196.7173	$196.72	$196.70	$196.70
Purchase #6	$218.42	5.824%	$231.1408	$231.14	$231.15	$231.10
Purchase #7	$212.87	11.505%	$237.3607	$237.36	$237.35	$237.40
7 purchase totals =	$936.70		$1,011.3434	$1,011.34	$1,011.35	$1,011.30