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	$179.71	4.390%	$187.5993	$187.60	$187.60	$187.60
Purchase #2	$124.37	9.624%	$136.3394	$136.34	$136.35	$136.30
Purchase #3	$168.40	4.155%	$175.397	$175.40	$175.40	$175.40
Purchase #4	$119.67	11.332%	$133.231	$133.23	$133.25	$133.20
Purchase #5	$146.89	13.133%	$166.1811	$166.18	$166.20	$166.20
Purchase #6	$123.96	13.384%	$140.5508	$140.55	$140.55	$140.60
Purchase #7	$138.86	4.505%	$145.1156	$145.12	$145.10	$145.10
7 purchase totals =	$1,001.86		$1,084.4142	$1,084.42	$1,084.45	$1,084.40