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	$192.72	9.681%	$211.3772	$211.38	$211.40	$211.40
Purchase #2	$242.87	12.567%	$273.3915	$273.39	$273.40	$273.40
Purchase #3	$168.35	12.498%	$189.3904	$189.39	$189.40	$189.40
Purchase #4	$68.56	11.320%	$76.321	$76.32	$76.30	$76.30
Purchase #5	$10.61	4.609%	$11.099	$11.10	$11.10	$11.10
Purchase #6	$148.69	11.261%	$165.434	$165.43	$165.45	$165.40
Purchase #7	$196.85	12.730%	$221.909	$221.91	$221.90	$221.90
7 purchase totals =	$1,028.65		$1,148.9221	$1,148.92	$1,148.95	$1,148.90