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	$241.65	5.611%	$255.209	$255.21	$255.20	$255.20
Purchase #2	$54.54	8.776%	$59.3264	$59.33	$59.35	$59.30
Purchase #3	$150.36	6.467%	$160.0838	$160.08	$160.10	$160.10
Purchase #4	$169.37	5.623%	$178.8937	$178.89	$178.90	$178.90
Purchase #5	$87.86	4.544%	$91.8524	$91.85	$91.85	$91.90
Purchase #6	$168.46	7.585%	$181.2377	$181.24	$181.25	$181.20
Purchase #7	$229.68	5.451%	$242.1999	$242.20	$242.20	$242.20
7 purchase totals =	$1,101.92		$1,168.8029	$1,168.80	$1,168.85	$1,168.80