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	$134.81	6.334%	$143.3489	$143.35	$143.35	$143.30
Purchase #2	$205.31	4.430%	$214.4052	$214.41	$214.40	$214.40
Purchase #3	$61.79	4.780%	$64.7436	$64.74	$64.75	$64.70
Purchase #4	$169.41	4.167%	$176.4693	$176.47	$176.45	$176.50
Purchase #5	$48.76	13.262%	$55.2266	$55.23	$55.25	$55.20
Purchase #6	$213.73	5.437%	$225.3505	$225.35	$225.35	$225.40
Purchase #7	$246.59	7.420%	$264.887	$264.89	$264.90	$264.90
7 purchase totals =	$1,080.40		$1,144.4311	$1,144.44	$1,144.45	$1,144.40