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	$92.96	8.320%	$100.6943	$100.69	$100.70	$100.70
Purchase #2	$55.52	12.488%	$62.4533	$62.45	$62.45	$62.50
Purchase #3	$217.34	5.638%	$229.5936	$229.59	$229.60	$229.60
Purchase #4	$120.47	8.358%	$130.5389	$130.54	$130.55	$130.50
Purchase #5	$109.72	5.615%	$115.8808	$115.88	$115.90	$115.90
Purchase #6	$140.37	12.179%	$157.4657	$157.47	$157.45	$157.50
Purchase #7	$201.54	9.674%	$221.037	$221.04	$221.05	$221.00
7 purchase totals =	$937.92		$1,017.6636	$1,017.66	$1,017.70	$1,017.70