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	$178.88	11.423%	$199.3135	$199.31	$199.30	$199.30
Purchase #2	$11.81	6.223%	$12.5449	$12.54	$12.55	$12.50
Purchase #3	$96.43	7.363%	$103.5301	$103.53	$103.55	$103.50
Purchase #4	$37.53	4.581%	$39.2492	$39.25	$39.25	$39.20
Purchase #5	$197.38	6.486%	$210.1821	$210.18	$210.20	$210.20
Purchase #6	$99.69	12.189%	$111.8412	$111.84	$111.85	$111.80
Purchase #7	$50.30	12.111%	$56.3918	$56.39	$56.40	$56.40
7 purchase totals =	$672.02		$733.0528	$733.04	$733.10	$732.90