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	$172.38	8.352%	$186.7772	$186.78	$186.80	$186.80
Purchase #2	$184.76	3.604%	$191.4188	$191.42	$191.40	$191.40
Purchase #3	$246.33	3.538%	$255.0452	$255.05	$255.05	$255.00
Purchase #4	$195.43	10.366%	$215.6883	$215.69	$215.70	$215.70
Purchase #5	$59.45	13.516%	$67.4853	$67.49	$67.50	$67.50
Purchase #6	$173.76	6.729%	$185.4523	$185.45	$185.45	$185.50
Purchase #7	$244.63	6.553%	$260.6606	$260.66	$260.65	$260.70
7 purchase totals =	$1,276.74		$1,362.5277	$1,362.54	$1,362.55	$1,362.60