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	$70.58	3.332%	$72.9317	$72.93	$72.95	$72.90
Purchase #2	$152.61	9.592%	$167.2484	$167.25	$167.25	$167.20
Purchase #3	$19.83	7.116%	$21.2411	$21.24	$21.25	$21.20
Purchase #4	$11.56	12.210%	$12.9715	$12.97	$12.95	$13.00
Purchase #5	$234.31	4.697%	$245.3155	$245.32	$245.30	$245.30
Purchase #6	$233.51	9.735%	$256.2422	$256.24	$256.25	$256.20
Purchase #7	$203.34	7.423%	$218.4339	$218.43	$218.45	$218.40
7 purchase totals =	$925.74		$994.3843	$994.38	$994.40	$994.20