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	$82.68	10.811%	$91.6185	$91.62	$91.60	$91.60
Purchase #2	$120.89	7.587%	$130.0619	$130.06	$130.05	$130.10
Purchase #3	$206.86	8.717%	$224.892	$224.89	$224.90	$224.90
Purchase #4	$78.55	9.712%	$86.1788	$86.18	$86.20	$86.20
Purchase #5	$53.47	3.372%	$55.273	$55.27	$55.25	$55.30
Purchase #6	$51.60	9.197%	$56.3457	$56.35	$56.35	$56.30
Purchase #7	$199.41	12.563%	$224.4619	$224.46	$224.45	$224.50
7 purchase totals =	$793.46		$868.8318	$868.83	$868.80	$868.90