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	$67.59	5.600%	$71.375	$71.38	$71.40	$71.40
Purchase #2	$26.57	4.840%	$27.856	$27.86	$27.85	$27.90
Purchase #3	$69.60	4.293%	$72.5879	$72.59	$72.60	$72.60
Purchase #4	$226.80	13.849%	$258.2095	$258.21	$258.20	$258.20
Purchase #5	$224.49	7.234%	$240.7296	$240.73	$240.75	$240.70
Purchase #6	$36.32	5.163%	$38.1952	$38.20	$38.20	$38.20
Purchase #7	$131.66	10.393%	$145.3434	$145.34	$145.35	$145.30
7 purchase totals =	$783.03		$854.2966	$854.31	$854.35	$854.30