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	$204.43	6.774%	$218.2781	$218.28	$218.30	$218.30
Purchase #2	$17.68	5.469%	$18.6469	$18.65	$18.65	$18.60
Purchase #3	$99.29	13.497%	$112.6912	$112.69	$112.70	$112.70
Purchase #4	$200.90	7.161%	$215.2864	$215.29	$215.30	$215.30
Purchase #5	$49.44	12.112%	$55.4282	$55.43	$55.45	$55.40
Purchase #6	$230.54	12.263%	$258.8111	$258.81	$258.80	$258.80
Purchase #7	$67.88	6.482%	$72.28	$72.28	$72.30	$72.30
7 purchase totals =	$870.16		$951.4219	$951.43	$951.50	$951.40