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	$176.88	7.570%	$190.2698	$190.27	$190.25	$190.30
Purchase #2	$147.93	12.531%	$166.4671	$166.47	$166.45	$166.50
Purchase #3	$158.71	3.555%	$164.3521	$164.35	$164.35	$164.40
Purchase #4	$32.65	8.164%	$35.3155	$35.32	$35.30	$35.30
Purchase #5	$137.92	11.207%	$153.3767	$153.38	$153.40	$153.40
Purchase #6	$165.92	12.428%	$186.5405	$186.54	$186.55	$186.50
Purchase #7	$96.68	13.210%	$109.4514	$109.45	$109.45	$109.50
7 purchase totals =	$916.69		$1,005.7731	$1,005.78	$1,005.75	$1,005.90