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	$124.67	7.688%	$134.2546	$134.25	$134.25	$134.30
Purchase #2	$161.54	4.205%	$168.3328	$168.33	$168.35	$168.30
Purchase #3	$245.73	12.671%	$276.8664	$276.87	$276.85	$276.90
Purchase #4	$123.49	11.520%	$137.716	$137.72	$137.70	$137.70
Purchase #5	$208.37	3.814%	$216.3172	$216.32	$216.30	$216.30
Purchase #6	$58.81	10.830%	$65.1791	$65.18	$65.20	$65.20
Purchase #7	$111.85	10.353%	$123.4298	$123.43	$123.45	$123.40
7 purchase totals =	$1,034.46		$1,122.0959	$1,122.10	$1,122.10	$1,122.10