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	$187.85	5.609%	$198.3865	$198.39	$198.40	$198.40
Purchase #2	$101.33	4.649%	$106.0408	$106.04	$106.05	$106.00
Purchase #3	$168.86	6.451%	$179.7532	$179.75	$179.75	$179.80
Purchase #4	$217.41	10.630%	$240.5207	$240.52	$240.50	$240.50
Purchase #5	$22.35	9.164%	$24.3982	$24.40	$24.40	$24.40
Purchase #6	$55.77	6.442%	$59.3627	$59.36	$59.35	$59.40
Purchase #7	$50.31	5.515%	$53.0846	$53.08	$53.10	$53.10
7 purchase totals =	$803.88		$861.5467	$861.54	$861.55	$861.60