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	$235.48	11.397%	$262.3177	$262.32	$262.30	$262.30
Purchase #2	$63.63	5.522%	$67.1436	$67.14	$67.15	$67.10
Purchase #3	$216.84	5.390%	$228.5277	$228.53	$228.55	$228.50
Purchase #4	$191.66	8.496%	$207.9434	$207.94	$207.95	$207.90
Purchase #5	$84.55	5.681%	$89.3533	$89.35	$89.35	$89.40
Purchase #6	$204.52	8.661%	$222.2335	$222.23	$222.25	$222.20
Purchase #7	$227.41	12.598%	$256.0591	$256.06	$256.05	$256.10
7 purchase totals =	$1,224.09		$1,333.5783	$1,333.57	$1,333.60	$1,333.50