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	$136.85	6.410%	$145.6221	$145.62	$145.60	$145.60
Purchase #2	$202.64	5.201%	$213.1793	$213.18	$213.20	$213.20
Purchase #3	$153.65	10.274%	$169.436	$169.44	$169.45	$169.40
Purchase #4	$118.47	7.320%	$127.142	$127.14	$127.15	$127.10
Purchase #5	$136.50	6.432%	$145.2797	$145.28	$145.30	$145.30
Purchase #6	$228.86	13.110%	$258.8635	$258.86	$258.85	$258.90
Purchase #7	$55.89	6.152%	$59.3284	$59.33	$59.35	$59.30
7 purchase totals =	$1,032.86		$1,118.8510	$1,118.85	$1,118.90	$1,118.80