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	$114.99	3.133%	$118.5926	$118.59	$118.60	$118.60
Purchase #2	$163.46	3.155%	$168.6172	$168.62	$168.60	$168.60
Purchase #3	$121.37	9.760%	$133.2157	$133.22	$133.20	$133.20
Purchase #4	$197.25	5.871%	$208.8305	$208.83	$208.85	$208.80
Purchase #5	$77.53	6.380%	$82.4764	$82.48	$82.50	$82.50
Purchase #6	$79.70	12.508%	$89.6689	$89.67	$89.65	$89.70
Purchase #7	$178.46	12.740%	$201.1958	$201.20	$201.20	$201.20
7 purchase totals =	$932.76		$1,002.5971	$1,002.61	$1,002.60	$1,002.60