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	$145.94	11.482%	$162.6968	$162.70	$162.70	$162.70
Purchase #2	$176.63	8.188%	$191.0925	$191.09	$191.10	$191.10
Purchase #3	$175.58	3.579%	$181.864	$181.86	$181.85	$181.90
Purchase #4	$231.52	3.740%	$240.1788	$240.18	$240.20	$240.20
Purchase #5	$138.80	8.397%	$150.455	$150.46	$150.45	$150.50
Purchase #6	$23.35	6.728%	$24.921	$24.92	$24.90	$24.90
Purchase #7	$63.73	5.647%	$67.3288	$67.33	$67.35	$67.30
7 purchase totals =	$955.55		$1,018.5369	$1,018.54	$1,018.55	$1,018.60