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	$95.70	11.740%	$106.9352	$106.94	$106.95	$106.90
Purchase #2	$177.71	4.797%	$186.2347	$186.23	$186.25	$186.20
Purchase #3	$29.25	13.225%	$33.1183	$33.12	$33.10	$33.10
Purchase #4	$151.96	3.702%	$157.5856	$157.59	$157.60	$157.60
Purchase #5	$62.93	13.683%	$71.5407	$71.54	$71.55	$71.50
Purchase #6	$235.88	8.332%	$255.5335	$255.53	$255.55	$255.50
Purchase #7	$105.98	6.297%	$112.6536	$112.65	$112.65	$112.70
7 purchase totals =	$859.41		$923.6016	$923.60	$923.65	$923.50