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	$152.80	8.818%	$166.2739	$166.27	$166.25	$166.30
Purchase #2	$152.93	7.616%	$164.5771	$164.58	$164.60	$164.60
Purchase #3	$174.87	13.494%	$198.467	$198.47	$198.45	$198.50
Purchase #4	$29.87	6.843%	$31.914	$31.91	$31.90	$31.90
Purchase #5	$178.71	11.139%	$198.6165	$198.62	$198.60	$198.60
Purchase #6	$13.93	8.698%	$15.1416	$15.14	$15.15	$15.10
Purchase #7	$18.81	7.806%	$20.2783	$20.28	$20.30	$20.30
7 purchase totals =	$721.92		$795.2684	$795.27	$795.25	$795.30