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	$241.33	6.480%	$256.9682	$256.97	$256.95	$257.00
Purchase #2	$182.59	4.223%	$190.3008	$190.30	$190.30	$190.30
Purchase #3	$147.42	7.218%	$158.0608	$158.06	$158.05	$158.10
Purchase #4	$102.39	9.316%	$111.9287	$111.93	$111.95	$111.90
Purchase #5	$233.38	7.248%	$250.2954	$250.30	$250.30	$250.30
Purchase #6	$242.71	4.444%	$253.496	$253.50	$253.50	$253.50
Purchase #7	$176.51	10.529%	$195.0947	$195.09	$195.10	$195.10
7 purchase totals =	$1,326.33		$1,416.1446	$1,416.15	$1,416.15	$1,416.20