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	$159.48	12.208%	$178.9493	$178.95	$178.95	$178.90
Purchase #2	$30.27	9.354%	$33.1015	$33.10	$33.10	$33.10
Purchase #3	$132.91	13.141%	$150.3757	$150.38	$150.40	$150.40
Purchase #4	$27.33	3.661%	$28.3306	$28.33	$28.35	$28.30
Purchase #5	$152.83	13.697%	$173.7631	$173.76	$173.75	$173.80
Purchase #6	$131.94	11.456%	$147.055	$147.06	$147.05	$147.10
Purchase #7	$68.78	4.177%	$71.6529	$71.65	$71.65	$71.70
7 purchase totals =	$703.54		$783.2281	$783.23	$783.25	$783.30