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	$179.28	6.176%	$190.3523	$190.35	$190.35	$190.40
Purchase #2	$248.29	9.294%	$271.3661	$271.37	$271.35	$271.40
Purchase #3	$93.37	7.346%	$100.229	$100.23	$100.25	$100.20
Purchase #4	$79.90	13.314%	$90.5379	$90.54	$90.55	$90.50
Purchase #5	$37.26	3.123%	$38.4236	$38.42	$38.40	$38.40
Purchase #6	$238.35	4.541%	$249.1735	$249.17	$249.15	$249.20
Purchase #7	$98.82	3.373%	$102.1532	$102.15	$102.15	$102.20
7 purchase totals =	$975.27		$1,042.2356	$1,042.23	$1,042.20	$1,042.30