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	$158.50	5.856%	$167.7818	$167.78	$167.80	$167.80
Purchase #2	$208.86	12.728%	$235.4437	$235.44	$235.45	$235.40
Purchase #3	$151.92	10.662%	$168.1177	$168.12	$168.10	$168.10
Purchase #4	$150.38	10.573%	$166.2797	$166.28	$166.30	$166.30
Purchase #5	$115.63	6.848%	$123.5483	$123.55	$123.55	$123.50
Purchase #6	$24.50	11.535%	$27.3261	$27.33	$27.35	$27.30
Purchase #7	$209.41	9.629%	$229.5741	$229.57	$229.55	$229.60
7 purchase totals =	$1,019.20		$1,118.0714	$1,118.07	$1,118.10	$1,118.00