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	$72.71	13.268%	$82.3572	$82.36	$82.35	$82.40
Purchase #2	$8.92	12.511%	$10.036	$10.04	$10.05	$10.00
Purchase #3	$60.59	3.141%	$62.4931	$62.49	$62.50	$62.50
Purchase #4	$28.68	6.352%	$30.5018	$30.50	$30.50	$30.50
Purchase #5	$60.71	12.567%	$68.3394	$68.34	$68.35	$68.30
Purchase #6	$228.29	5.811%	$241.5559	$241.56	$241.55	$241.60
Purchase #7	$42.93	5.744%	$45.3959	$45.40	$45.40	$45.40
7 purchase totals =	$502.83		$540.6793	$540.69	$540.70	$540.70