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	$210.30	12.484%	$236.5539	$236.55	$236.55	$236.60
Purchase #2	$100.81	10.509%	$111.4041	$111.40	$111.40	$111.40
Purchase #3	$109.63	9.844%	$120.422	$120.42	$120.40	$120.40
Purchase #4	$185.95	7.733%	$200.3295	$200.33	$200.35	$200.30
Purchase #5	$28.65	7.848%	$30.8985	$30.90	$30.90	$30.90
Purchase #6	$242.61	8.605%	$263.4866	$263.49	$263.50	$263.50
Purchase #7	$42.86	12.617%	$48.2676	$48.27	$48.25	$48.30
7 purchase totals =	$920.81		$1,011.3622	$1,011.36	$1,011.35	$1,011.40