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	$148.54	4.374%	$155.0371	$155.04	$155.05	$155.00
Purchase #2	$91.85	9.671%	$100.7328	$100.73	$100.75	$100.70
Purchase #3	$10.96	10.225%	$12.0807	$12.08	$12.10	$12.10
Purchase #4	$124.60	3.136%	$128.5075	$128.51	$128.50	$128.50
Purchase #5	$141.65	7.738%	$152.6109	$152.61	$152.60	$152.60
Purchase #6	$174.76	13.577%	$198.4872	$198.49	$198.50	$198.50
Purchase #7	$215.96	12.795%	$243.5921	$243.59	$243.60	$243.60
7 purchase totals =	$908.32		$991.0483	$991.05	$991.10	$991.00