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	$134.50	10.225%	$148.2526	$148.25	$148.25	$148.30
Purchase #2	$244.29	12.271%	$274.2668	$274.27	$274.25	$274.30
Purchase #3	$58.74	6.422%	$62.5123	$62.51	$62.50	$62.50
Purchase #4	$62.49	8.632%	$67.8841	$67.88	$67.90	$67.90
Purchase #5	$250.43	12.263%	$281.1402	$281.14	$281.15	$281.10
Purchase #6	$228.94	13.811%	$260.5589	$260.56	$260.55	$260.60
Purchase #7	$125.27	6.359%	$133.2359	$133.24	$133.25	$133.20
7 purchase totals =	$1,104.66		$1,227.8508	$1,227.85	$1,227.85	$1,227.90