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	$22.64	6.465%	$24.1037	$24.10	$24.10	$24.10
Purchase #2	$187.39	6.312%	$199.2181	$199.22	$199.20	$199.20
Purchase #3	$194.51	10.687%	$215.2973	$215.30	$215.30	$215.30
Purchase #4	$108.88	13.777%	$123.8804	$123.88	$123.90	$123.90
Purchase #5	$43.74	6.369%	$46.5258	$46.53	$46.55	$46.50
Purchase #6	$217.76	10.243%	$240.0652	$240.07	$240.05	$240.10
Purchase #7	$89.60	7.527%	$96.3442	$96.34	$96.35	$96.30
7 purchase totals =	$864.52		$945.4347	$945.44	$945.45	$945.40