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	$165.77	10.762%	$183.6102	$183.61	$183.60	$183.60
Purchase #2	$96.40	13.725%	$109.6309	$109.63	$109.65	$109.60
Purchase #3	$249.33	7.209%	$267.3042	$267.30	$267.30	$267.30
Purchase #4	$99.55	11.435%	$110.9335	$110.93	$110.95	$110.90
Purchase #5	$53.50	10.307%	$59.0142	$59.01	$59.00	$59.00
Purchase #6	$182.61	12.430%	$205.3084	$205.31	$205.30	$205.30
Purchase #7	$105.31	10.484%	$116.3507	$116.35	$116.35	$116.40
7 purchase totals =	$952.47		$1,052.1521	$1,052.14	$1,052.15	$1,052.10