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	$230.94	6.200%	$245.2583	$245.26	$245.25	$245.30
Purchase #2	$18.39	5.308%	$19.3661	$19.37	$19.35	$19.40
Purchase #3	$58.87	11.871%	$65.8585	$65.86	$65.85	$65.90
Purchase #4	$184.79	12.302%	$207.5229	$207.52	$207.50	$207.50
Purchase #5	$164.94	12.340%	$185.2936	$185.29	$185.30	$185.30
Purchase #6	$218.54	5.836%	$231.294	$231.29	$231.30	$231.30
Purchase #7	$124.65	5.726%	$131.7875	$131.79	$131.80	$131.80
7 purchase totals =	$1,001.12		$1,086.3809	$1,086.38	$1,086.35	$1,086.50