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	$56.80	4.113%	$59.1362	$59.14	$59.15	$59.10
Purchase #2	$137.48	5.433%	$144.9493	$144.95	$144.95	$144.90
Purchase #3	$131.70	4.728%	$137.9268	$137.93	$137.95	$137.90
Purchase #4	$234.85	5.142%	$246.926	$246.93	$246.95	$246.90
Purchase #5	$217.96	11.433%	$242.8794	$242.88	$242.90	$242.90
Purchase #6	$61.64	12.831%	$69.549	$69.55	$69.55	$69.50
Purchase #7	$155.74	8.797%	$169.4404	$169.44	$169.45	$169.40
7 purchase totals =	$996.17		$1,070.8071	$1,070.82	$1,070.90	$1,070.60