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	$148.78	11.850%	$166.4104	$166.41	$166.40	$166.40
Purchase #2	$101.30	8.417%	$109.8264	$109.83	$109.85	$109.80
Purchase #3	$207.83	4.604%	$217.3985	$217.40	$217.40	$217.40
Purchase #4	$44.35	3.641%	$45.9648	$45.96	$45.95	$46.00
Purchase #5	$133.56	10.600%	$147.7174	$147.72	$147.70	$147.70
Purchase #6	$163.68	6.818%	$174.8397	$174.84	$174.85	$174.80
Purchase #7	$216.51	8.278%	$234.4327	$234.43	$234.45	$234.40
7 purchase totals =	$1,016.01		$1,096.5899	$1,096.59	$1,096.60	$1,096.50