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	$63.25	12.732%	$71.303	$71.30	$71.30	$71.30
Purchase #2	$184.77	6.528%	$196.8318	$196.83	$196.85	$196.80
Purchase #3	$204.44	6.726%	$218.1906	$218.19	$218.20	$218.20
Purchase #4	$250.64	7.548%	$269.5583	$269.56	$269.55	$269.60
Purchase #5	$196.30	5.555%	$207.2045	$207.20	$207.20	$207.20
Purchase #6	$238.55	8.157%	$258.0085	$258.01	$258.00	$258.00
Purchase #7	$246.81	12.803%	$278.4091	$278.41	$278.40	$278.40
7 purchase totals =	$1,384.76		$1,499.5058	$1,499.50	$1,499.50	$1,499.50