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	$222.72	11.125%	$247.4976	$247.50	$247.50	$247.50
Purchase #2	$91.76	9.740%	$100.6974	$100.70	$100.70	$100.70
Purchase #3	$215.92	12.568%	$243.0568	$243.06	$243.05	$243.10
Purchase #4	$24.69	4.730%	$25.8578	$25.86	$25.85	$25.90
Purchase #5	$72.89	4.391%	$76.0906	$76.09	$76.10	$76.10
Purchase #6	$250.56	4.376%	$261.5245	$261.52	$261.50	$261.50
Purchase #7	$188.43	9.169%	$205.7071	$205.71	$205.70	$205.70
7 purchase totals =	$1,066.97		$1,160.4318	$1,160.44	$1,160.40	$1,160.50