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	$244.98	10.835%	$271.5236	$271.52	$271.50	$271.50
Purchase #2	$221.97	10.419%	$245.0971	$245.10	$245.10	$245.10
Purchase #3	$55.64	11.745%	$62.1749	$62.17	$62.15	$62.20
Purchase #4	$93.35	7.813%	$100.6434	$100.64	$100.65	$100.60
Purchase #5	$20.87	4.557%	$21.821	$21.82	$21.80	$21.80
Purchase #6	$105.61	9.658%	$115.8098	$115.81	$115.80	$115.80
Purchase #7	$193.46	10.739%	$214.2357	$214.24	$214.25	$214.20
7 purchase totals =	$935.88		$1,031.3055	$1,031.30	$1,031.25	$1,031.20