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	$108.46	9.827%	$119.1184	$119.12	$119.10	$119.10
Purchase #2	$94.87	13.316%	$107.5029	$107.50	$107.50	$107.50
Purchase #3	$61.76	12.818%	$69.6764	$69.68	$69.70	$69.70
Purchase #4	$116.72	12.534%	$131.3497	$131.35	$131.35	$131.30
Purchase #5	$105.39	5.516%	$111.2033	$111.20	$111.20	$111.20
Purchase #6	$142.83	6.798%	$152.5396	$152.54	$152.55	$152.50
Purchase #7	$191.46	13.781%	$217.8451	$217.85	$217.85	$217.80
7 purchase totals =	$821.49		$909.2354	$909.24	$909.25	$909.10