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	$151.68	8.215%	$164.1405	$164.14	$164.15	$164.10
Purchase #2	$236.82	9.579%	$259.505	$259.51	$259.50	$259.50
Purchase #3	$183.56	11.425%	$204.5317	$204.53	$204.55	$204.50
Purchase #4	$133.53	12.520%	$150.248	$150.25	$150.25	$150.20
Purchase #5	$54.67	12.479%	$61.4923	$61.49	$61.50	$61.50
Purchase #6	$28.50	8.809%	$31.0106	$31.01	$31.00	$31.00
Purchase #7	$63.64	13.186%	$72.0316	$72.03	$72.05	$72.00
7 purchase totals =	$852.40		$942.9597	$942.96	$943.00	$942.80