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	$145.46	11.543%	$162.2504	$162.25	$162.25	$162.30
Purchase #2	$35.57	9.528%	$38.9591	$38.96	$38.95	$39.00
Purchase #3	$213.89	11.428%	$238.3333	$238.33	$238.35	$238.30
Purchase #4	$209.84	4.284%	$218.8295	$218.83	$218.85	$218.80
Purchase #5	$221.50	5.301%	$233.2417	$233.24	$233.25	$233.20
Purchase #6	$54.71	10.465%	$60.4354	$60.44	$60.45	$60.40
Purchase #7	$87.59	7.621%	$94.2652	$94.27	$94.25	$94.30
7 purchase totals =	$968.56		$1,046.3146	$1,046.32	$1,046.35	$1,046.30