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	$85.77	5.318%	$90.3312	$90.33	$90.35	$90.30
Purchase #2	$101.77	3.241%	$105.0684	$105.07	$105.05	$105.10
Purchase #3	$236.52	9.154%	$258.171	$258.17	$258.15	$258.20
Purchase #4	$125.97	4.649%	$131.8263	$131.83	$131.85	$131.80
Purchase #5	$150.93	7.854%	$162.784	$162.78	$162.80	$162.80
Purchase #6	$232.97	5.836%	$246.5661	$246.57	$246.55	$246.60
Purchase #7	$191.64	3.545%	$198.4336	$198.43	$198.45	$198.40
7 purchase totals =	$1,125.57		$1,193.1806	$1,193.18	$1,193.20	$1,193.20