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	$169.48	7.259%	$181.7826	$181.78	$181.80	$181.80
Purchase #2	$57.42	9.236%	$62.7233	$62.72	$62.70	$62.70
Purchase #3	$215.30	7.343%	$231.1095	$231.11	$231.10	$231.10
Purchase #4	$143.71	6.362%	$152.8528	$152.85	$152.85	$152.90
Purchase #5	$102.51	8.602%	$111.3279	$111.33	$111.35	$111.30
Purchase #6	$163.74	8.681%	$177.9543	$177.95	$177.95	$178.00
Purchase #7	$79.34	8.577%	$86.145	$86.15	$86.15	$86.10
7 purchase totals =	$931.50		$1,003.8954	$1,003.89	$1,003.90	$1,003.90