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	$145.58	6.515%	$155.0645	$155.06	$155.05	$155.10
Purchase #2	$147.52	12.144%	$165.4348	$165.43	$165.45	$165.40
Purchase #3	$232.59	3.319%	$240.3097	$240.31	$240.30	$240.30
Purchase #4	$245.52	6.495%	$261.4665	$261.47	$261.45	$261.50
Purchase #5	$13.32	3.194%	$13.7454	$13.75	$13.75	$13.70
Purchase #6	$47.97	13.353%	$54.3754	$54.38	$54.40	$54.40
Purchase #7	$221.77	9.523%	$242.8892	$242.89	$242.90	$242.90
7 purchase totals =	$1,054.27		$1,133.2855	$1,133.29	$1,133.30	$1,133.30