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	$43.65	4.607%	$45.661	$45.66	$45.65	$45.70
Purchase #2	$43.93	9.678%	$48.1815	$48.18	$48.20	$48.20
Purchase #3	$89.30	7.691%	$96.1681	$96.17	$96.15	$96.20
Purchase #4	$154.81	9.470%	$169.4705	$169.47	$169.45	$169.50
Purchase #5	$38.44	4.454%	$40.1521	$40.15	$40.15	$40.20
Purchase #6	$137.86	6.790%	$147.2207	$147.22	$147.20	$147.20
Purchase #7	$133.95	12.167%	$150.2477	$150.25	$150.25	$150.20
7 purchase totals =	$641.94		$697.1016	$697.10	$697.05	$697.20