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	$74.43	9.559%	$81.5448	$81.54	$81.55	$81.50
Purchase #2	$189.48	3.668%	$196.4301	$196.43	$196.45	$196.40
Purchase #3	$190.45	6.452%	$202.7378	$202.74	$202.75	$202.70
Purchase #4	$232.81	6.574%	$248.1149	$248.11	$248.10	$248.10
Purchase #5	$53.52	10.322%	$59.0443	$59.04	$59.05	$59.00
Purchase #6	$199.25	5.674%	$210.5554	$210.56	$210.55	$210.60
Purchase #7	$184.65	8.597%	$200.5244	$200.52	$200.50	$200.50
7 purchase totals =	$1,124.59		$1,198.9517	$1,198.94	$1,198.95	$1,198.80