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	$78.55	8.814%	$85.4734	$85.47	$85.45	$85.50
Purchase #2	$112.59	10.385%	$124.2825	$124.28	$124.30	$124.30
Purchase #3	$128.54	11.661%	$143.529	$143.53	$143.55	$143.50
Purchase #4	$76.79	3.824%	$79.7264	$79.73	$79.75	$79.70
Purchase #5	$247.70	5.725%	$261.8808	$261.88	$261.90	$261.90
Purchase #6	$78.32	4.539%	$81.8749	$81.87	$81.85	$81.90
Purchase #7	$127.33	7.744%	$137.1904	$137.19	$137.20	$137.20
7 purchase totals =	$849.82		$913.9574	$913.95	$914.00	$914.00