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	$141.82	6.180%	$150.5845	$150.58	$150.60	$150.60
Purchase #2	$175.69	3.729%	$182.2415	$182.24	$182.25	$182.20
Purchase #3	$202.55	8.121%	$218.9991	$219.00	$219.00	$219.00
Purchase #4	$57.82	3.136%	$59.6332	$59.63	$59.65	$59.60
Purchase #5	$198.57	6.709%	$211.8921	$211.89	$211.90	$211.90
Purchase #6	$212.29	9.781%	$233.0541	$233.05	$233.05	$233.10
Purchase #7	$143.85	6.273%	$152.8737	$152.87	$152.85	$152.90
7 purchase totals =	$1,132.59		$1,209.2782	$1,209.26	$1,209.30	$1,209.30