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	$239.31	3.229%	$247.0373	$247.04	$247.05	$247.00
Purchase #2	$84.92	12.360%	$95.4161	$95.42	$95.40	$95.40
Purchase #3	$155.81	7.117%	$166.899	$166.90	$166.90	$166.90
Purchase #4	$158.85	4.102%	$165.366	$165.37	$165.35	$165.40
Purchase #5	$25.40	11.775%	$28.3909	$28.39	$28.40	$28.40
Purchase #6	$95.45	4.238%	$99.4952	$99.50	$99.50	$99.50
Purchase #7	$193.31	4.663%	$202.324	$202.32	$202.30	$202.30
7 purchase totals =	$953.05		$1,004.9285	$1,004.94	$1,004.90	$1,004.90