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	$55.67	6.761%	$59.4338	$59.43	$59.45	$59.40
Purchase #2	$112.79	13.441%	$127.9501	$127.95	$127.95	$128.00
Purchase #3	$78.52	5.773%	$83.053	$83.05	$83.05	$83.10
Purchase #4	$16.95	7.316%	$18.1901	$18.19	$18.20	$18.20
Purchase #5	$239.46	3.298%	$247.3574	$247.36	$247.35	$247.40
Purchase #6	$201.46	10.520%	$222.6536	$222.65	$222.65	$222.70
Purchase #7	$52.84	4.199%	$55.0588	$55.06	$55.05	$55.10
7 purchase totals =	$757.69		$813.6968	$813.69	$813.70	$813.90