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	$40.58	8.311%	$43.9526	$43.95	$43.95	$44.00
Purchase #2	$183.31	6.153%	$194.5891	$194.59	$194.60	$194.60
Purchase #3	$61.53	6.458%	$65.5036	$65.50	$65.50	$65.50
Purchase #4	$81.89	11.360%	$91.1927	$91.19	$91.20	$91.20
Purchase #5	$95.35	12.786%	$107.5415	$107.54	$107.55	$107.50
Purchase #6	$76.67	7.550%	$82.4586	$82.46	$82.45	$82.50
Purchase #7	$11.32	8.583%	$12.2916	$12.29	$12.30	$12.30
7 purchase totals =	$550.65		$597.5297	$597.52	$597.55	$597.60