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	$59.44	7.498%	$63.8968	$63.90	$63.90	$63.90
Purchase #2	$139.32	4.654%	$145.804	$145.80	$145.80	$145.80
Purchase #3	$28.41	7.805%	$30.6274	$30.63	$30.65	$30.60
Purchase #4	$147.69	13.284%	$167.3091	$167.31	$167.30	$167.30
Purchase #5	$100.88	8.506%	$109.4609	$109.46	$109.45	$109.50
Purchase #6	$85.74	5.367%	$90.3417	$90.34	$90.35	$90.30
Purchase #7	$106.90	7.340%	$114.7465	$114.75	$114.75	$114.70
7 purchase totals =	$668.38		$722.1864	$722.19	$722.20	$722.10