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	$178.75	3.649%	$185.2726	$185.27	$185.25	$185.30
Purchase #2	$210.97	5.566%	$222.7126	$222.71	$222.70	$222.70
Purchase #3	$14.91	11.348%	$16.602	$16.60	$16.60	$16.60
Purchase #4	$173.56	9.178%	$189.4893	$189.49	$189.50	$189.50
Purchase #5	$128.64	9.538%	$140.9097	$140.91	$140.90	$140.90
Purchase #6	$201.80	10.308%	$222.6015	$222.60	$222.60	$222.60
Purchase #7	$82.40	10.432%	$90.996	$91.00	$91.00	$91.00
7 purchase totals =	$991.03		$1,068.5837	$1,068.58	$1,068.55	$1,068.60