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	$56.80	8.833%	$61.8171	$61.82	$61.80	$61.80
Purchase #2	$224.69	12.695%	$253.2144	$253.21	$253.20	$253.20
Purchase #3	$178.90	11.182%	$198.9046	$198.90	$198.90	$198.90
Purchase #4	$39.62	9.302%	$43.3055	$43.31	$43.30	$43.30
Purchase #5	$137.86	7.546%	$148.2629	$148.26	$148.25	$148.30
Purchase #6	$110.73	11.411%	$123.3654	$123.37	$123.35	$123.40
Purchase #7	$186.35	5.505%	$196.6086	$196.61	$196.60	$196.60
7 purchase totals =	$934.95		$1,025.4785	$1,025.48	$1,025.40	$1,025.50