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	$160.83	8.551%	$174.5826	$174.58	$174.60	$174.60
Purchase #2	$61.94	7.646%	$66.6759	$66.68	$66.70	$66.70
Purchase #3	$12.64	10.867%	$14.0136	$14.01	$14.00	$14.00
Purchase #4	$45.70	11.301%	$50.8646	$50.86	$50.85	$50.90
Purchase #5	$17.63	3.815%	$18.3026	$18.30	$18.30	$18.30
Purchase #6	$160.39	4.216%	$167.152	$167.15	$167.15	$167.20
Purchase #7	$62.69	8.198%	$67.8293	$67.83	$67.85	$67.80
7 purchase totals =	$521.82		$559.4206	$559.41	$559.45	$559.50