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	$112.61	9.706%	$123.5399	$123.54	$123.55	$123.50
Purchase #2	$19.76	12.688%	$22.2671	$22.27	$22.25	$22.30
Purchase #3	$44.80	7.871%	$48.3262	$48.33	$48.35	$48.30
Purchase #4	$179.39	8.858%	$195.2804	$195.28	$195.30	$195.30
Purchase #5	$29.37	8.658%	$31.9129	$31.91	$31.90	$31.90
Purchase #6	$38.35	10.591%	$42.4116	$42.41	$42.40	$42.40
Purchase #7	$184.37	11.312%	$205.2259	$205.23	$205.25	$205.20
7 purchase totals =	$608.65		$668.9640	$668.97	$669.00	$668.90