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	$173.76	4.512%	$181.6001	$181.60	$181.60	$181.60
Purchase #2	$86.31	3.828%	$89.6139	$89.61	$89.60	$89.60
Purchase #3	$30.25	7.544%	$32.5321	$32.53	$32.55	$32.50
Purchase #4	$38.26	5.483%	$40.3578	$40.36	$40.35	$40.40
Purchase #5	$91.94	3.874%	$95.5018	$95.50	$95.50	$95.50
Purchase #6	$37.55	13.302%	$42.5449	$42.54	$42.55	$42.50
Purchase #7	$40.50	6.248%	$43.0304	$43.03	$43.05	$43.00
7 purchase totals =	$498.57		$525.1810	$525.17	$525.20	$525.10