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	$67.60	6.620%	$72.0751	$72.08	$72.10	$72.10
Purchase #2	$72.30	13.755%	$82.2449	$82.24	$82.25	$82.20
Purchase #3	$53.43	5.300%	$56.2618	$56.26	$56.25	$56.30
Purchase #4	$71.31	10.687%	$78.9309	$78.93	$78.95	$78.90
Purchase #5	$73.84	11.585%	$82.3944	$82.39	$82.40	$82.40
Purchase #6	$67.28	7.613%	$72.402	$72.40	$72.40	$72.40
Purchase #7	$20.32	4.198%	$21.173	$21.17	$21.15	$21.20
7 purchase totals =	$426.08		$465.4821	$465.47	$465.50	$465.50