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	$148.61	10.409%	$164.0788	$164.08	$164.10	$164.10
Purchase #2	$247.58	3.663%	$256.6489	$256.65	$256.65	$256.60
Purchase #3	$55.61	6.262%	$59.0923	$59.09	$59.10	$59.10
Purchase #4	$247.30	5.323%	$260.4638	$260.46	$260.45	$260.50
Purchase #5	$52.41	5.473%	$55.2784	$55.28	$55.30	$55.30
Purchase #6	$156.94	11.262%	$174.6146	$174.61	$174.60	$174.60
Purchase #7	$193.27	9.264%	$211.1745	$211.17	$211.15	$211.20
7 purchase totals =	$1,101.72		$1,181.3513	$1,181.34	$1,181.35	$1,181.40