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	$99.55	8.670%	$108.181	$108.18	$108.20	$108.20
Purchase #2	$60.86	3.566%	$63.0303	$63.03	$63.05	$63.00
Purchase #3	$71.81	13.324%	$81.378	$81.38	$81.40	$81.40
Purchase #4	$111.72	7.508%	$120.1079	$120.11	$120.10	$120.10
Purchase #5	$31.49	7.416%	$33.8253	$33.83	$33.85	$33.80
Purchase #6	$17.69	9.541%	$19.3778	$19.38	$19.40	$19.40
Purchase #7	$69.72	3.610%	$72.2369	$72.24	$72.25	$72.20
7 purchase totals =	$462.84		$498.1372	$498.15	$498.25	$498.10