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	$115.65	3.316%	$119.485	$119.49	$119.50	$119.50
Purchase #2	$226.36	10.672%	$250.5171	$250.52	$250.50	$250.50
Purchase #3	$68.65	4.108%	$71.4701	$71.47	$71.45	$71.50
Purchase #4	$194.34	5.552%	$205.1298	$205.13	$205.15	$205.10
Purchase #5	$46.62	4.660%	$48.7925	$48.79	$48.80	$48.80
Purchase #6	$73.69	11.774%	$82.3663	$82.37	$82.35	$82.40
Purchase #7	$147.55	13.726%	$167.8027	$167.80	$167.80	$167.80
7 purchase totals =	$872.86		$945.5635	$945.57	$945.55	$945.60