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	$12.97	12.759%	$14.6248	$14.62	$14.60	$14.60
Purchase #2	$31.51	8.109%	$34.0651	$34.07	$34.05	$34.10
Purchase #3	$123.93	13.328%	$140.4474	$140.45	$140.45	$140.40
Purchase #4	$66.30	7.596%	$71.3361	$71.34	$71.35	$71.30
Purchase #5	$82.72	4.210%	$86.2025	$86.20	$86.20	$86.20
Purchase #6	$121.90	5.128%	$128.151	$128.15	$128.15	$128.20
Purchase #7	$181.39	5.353%	$191.0998	$191.10	$191.10	$191.10
7 purchase totals =	$620.72		$665.9267	$665.93	$665.90	$665.90