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	$114.31	11.410%	$127.3528	$127.35	$127.35	$127.40
Purchase #2	$82.50	11.757%	$92.1995	$92.20	$92.20	$92.20
Purchase #3	$229.72	8.287%	$248.7569	$248.76	$248.75	$248.80
Purchase #4	$194.84	12.721%	$219.6256	$219.63	$219.65	$219.60
Purchase #5	$6.68	12.671%	$7.5264	$7.53	$7.55	$7.50
Purchase #6	$200.33	7.760%	$215.8756	$215.88	$215.90	$215.90
Purchase #7	$158.26	10.629%	$175.0815	$175.08	$175.10	$175.10
7 purchase totals =	$986.64		$1,086.4183	$1,086.43	$1,086.50	$1,086.50