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	$102.62	13.467%	$116.4398	$116.44	$116.45	$116.40
Purchase #2	$211.77	3.141%	$218.4217	$218.42	$218.40	$218.40
Purchase #3	$20.33	3.867%	$21.1162	$21.12	$21.10	$21.10
Purchase #4	$61.38	9.345%	$67.116	$67.12	$67.10	$67.10
Purchase #5	$104.27	3.754%	$108.1843	$108.18	$108.20	$108.20
Purchase #6	$79.97	3.669%	$82.9041	$82.90	$82.90	$82.90
Purchase #7	$130.96	6.780%	$139.8391	$139.84	$139.85	$139.80
7 purchase totals =	$711.30		$754.0212	$754.02	$754.00	$753.90