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	$245.53	4.364%	$256.2449	$256.24	$256.25	$256.20
Purchase #2	$140.53	8.465%	$152.4259	$152.43	$152.45	$152.40
Purchase #3	$33.60	13.821%	$38.2439	$38.24	$38.25	$38.20
Purchase #4	$197.26	12.481%	$221.88	$221.88	$221.90	$221.90
Purchase #5	$99.75	12.657%	$112.3754	$112.38	$112.40	$112.40
Purchase #6	$107.34	6.568%	$114.3901	$114.39	$114.40	$114.40
Purchase #7	$218.71	13.822%	$248.9401	$248.94	$248.95	$248.90
7 purchase totals =	$1,042.72		$1,144.5003	$1,144.50	$1,144.60	$1,144.40