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	$143.95	8.342%	$155.9583	$155.96	$155.95	$156.00
Purchase #2	$59.32	5.686%	$62.6929	$62.69	$62.70	$62.70
Purchase #3	$50.27	3.548%	$52.0536	$52.05	$52.05	$52.10
Purchase #4	$180.71	3.404%	$186.8614	$186.86	$186.85	$186.90
Purchase #5	$82.79	5.478%	$87.3252	$87.33	$87.35	$87.30
Purchase #6	$43.65	3.419%	$45.1424	$45.14	$45.15	$45.10
Purchase #7	$186.32	4.524%	$194.7491	$194.75	$194.75	$194.70
7 purchase totals =	$747.01		$784.7829	$784.78	$784.80	$784.80