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	$183.31	4.813%	$192.1327	$192.13	$192.15	$192.10
Purchase #2	$220.78	10.164%	$243.2201	$243.22	$243.20	$243.20
Purchase #3	$40.42	12.195%	$45.3492	$45.35	$45.35	$45.30
Purchase #4	$249.89	11.689%	$279.0996	$279.10	$279.10	$279.10
Purchase #5	$103.38	11.540%	$115.3101	$115.31	$115.30	$115.30
Purchase #6	$12.28	7.640%	$13.2182	$13.22	$13.20	$13.20
Purchase #7	$42.70	6.232%	$45.3611	$45.36	$45.35	$45.40
7 purchase totals =	$852.76		$933.6910	$933.69	$933.65	$933.60