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	$131.50	7.285%	$141.0798	$141.08	$141.10	$141.10
Purchase #2	$140.44	13.873%	$159.9232	$159.92	$159.90	$159.90
Purchase #3	$166.58	9.469%	$182.3535	$182.35	$182.35	$182.40
Purchase #4	$123.26	11.774%	$137.7726	$137.77	$137.75	$137.80
Purchase #5	$180.28	13.415%	$204.4646	$204.46	$204.45	$204.50
Purchase #6	$144.57	12.405%	$162.5039	$162.50	$162.50	$162.50
Purchase #7	$99.69	3.391%	$103.0705	$103.07	$103.05	$103.10
7 purchase totals =	$986.32		$1,091.1681	$1,091.15	$1,091.10	$1,091.30