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	$9.52	11.836%	$10.6468	$10.65	$10.65	$10.60
Purchase #2	$81.76	12.127%	$91.675	$91.68	$91.70	$91.70
Purchase #3	$161.94	3.653%	$167.8557	$167.86	$167.85	$167.90
Purchase #4	$93.92	6.594%	$100.1131	$100.11	$100.10	$100.10
Purchase #5	$41.65	5.183%	$43.8087	$43.81	$43.80	$43.80
Purchase #6	$38.29	5.410%	$40.3615	$40.36	$40.35	$40.40
Purchase #7	$17.64	5.653%	$18.6372	$18.64	$18.65	$18.60
7 purchase totals =	$444.72		$473.0980	$473.11	$473.10	$473.10