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	$58.91	3.314%	$60.8623	$60.86	$60.85	$60.90
Purchase #2	$111.85	13.757%	$127.2372	$127.24	$127.25	$127.20
Purchase #3	$196.53	13.744%	$223.5411	$223.54	$223.55	$223.50
Purchase #4	$243.55	11.841%	$272.3888	$272.39	$272.40	$272.40
Purchase #5	$237.91	9.346%	$260.1451	$260.15	$260.15	$260.10
Purchase #6	$38.63	8.578%	$41.9437	$41.94	$41.95	$41.90
Purchase #7	$36.38	13.228%	$41.1923	$41.19	$41.20	$41.20
7 purchase totals =	$923.76		$1,027.3105	$1,027.31	$1,027.35	$1,027.20