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	$184.67	3.500%	$191.1335	$191.13	$191.15	$191.10
Purchase #2	$99.82	13.868%	$113.663	$113.66	$113.65	$113.70
Purchase #3	$225.90	13.276%	$255.8905	$255.89	$255.90	$255.90
Purchase #4	$117.40	6.127%	$124.5931	$124.59	$124.60	$124.60
Purchase #5	$170.78	9.595%	$187.1663	$187.17	$187.15	$187.20
Purchase #6	$85.27	13.591%	$96.859	$96.86	$96.85	$96.90
Purchase #7	$129.61	4.364%	$135.2662	$135.27	$135.25	$135.30
7 purchase totals =	$1,013.45		$1,104.5716	$1,104.57	$1,104.55	$1,104.70