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	$97.77	7.646%	$105.2455	$105.25	$105.25	$105.20
Purchase #2	$143.80	9.268%	$157.1274	$157.13	$157.15	$157.10
Purchase #3	$221.63	12.848%	$250.105	$250.11	$250.10	$250.10
Purchase #4	$26.33	7.724%	$28.3637	$28.36	$28.35	$28.40
Purchase #5	$137.76	13.561%	$156.4416	$156.44	$156.45	$156.40
Purchase #6	$250.37	5.782%	$264.8464	$264.85	$264.85	$264.80
Purchase #7	$38.25	12.578%	$43.0611	$43.06	$43.05	$43.10
7 purchase totals =	$915.91		$1,005.1907	$1,005.20	$1,005.20	$1,005.10