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	$41.34	5.731%	$43.7092	$43.71	$43.70	$43.70
Purchase #2	$55.55	12.663%	$62.5843	$62.58	$62.60	$62.60
Purchase #3	$201.33	6.572%	$214.5614	$214.56	$214.55	$214.60
Purchase #4	$171.81	3.383%	$177.6223	$177.62	$177.60	$177.60
Purchase #5	$37.64	8.698%	$40.9139	$40.91	$40.90	$40.90
Purchase #6	$209.66	6.372%	$223.0195	$223.02	$223.00	$223.00
Purchase #7	$40.59	11.374%	$45.2067	$45.21	$45.20	$45.20
7 purchase totals =	$757.92		$807.6173	$807.61	$807.55	$807.60