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	$35.55	8.214%	$38.4701	$38.47	$38.45	$38.50
Purchase #2	$155.83	7.559%	$167.6092	$167.61	$167.60	$167.60
Purchase #3	$121.94	4.600%	$127.5492	$127.55	$127.55	$127.50
Purchase #4	$93.97	11.482%	$104.7596	$104.76	$104.75	$104.80
Purchase #5	$198.72	8.391%	$215.3946	$215.39	$215.40	$215.40
Purchase #6	$215.64	13.830%	$245.463	$245.46	$245.45	$245.50
Purchase #7	$33.41	11.393%	$37.2164	$37.22	$37.20	$37.20
7 purchase totals =	$855.06		$936.4621	$936.46	$936.40	$936.50