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	$98.25	6.497%	$104.6333	$104.63	$104.65	$104.60
Purchase #2	$134.64	11.508%	$150.1344	$150.13	$150.15	$150.10
Purchase #3	$115.66	6.653%	$123.3549	$123.35	$123.35	$123.40
Purchase #4	$11.95	11.119%	$13.2787	$13.28	$13.30	$13.30
Purchase #5	$12.93	8.121%	$13.98	$13.98	$14.00	$14.00
Purchase #6	$73.84	6.693%	$78.7821	$78.78	$78.80	$78.80
Purchase #7	$237.92	8.586%	$258.3478	$258.35	$258.35	$258.30
7 purchase totals =	$685.19		$742.5112	$742.50	$742.60	$742.50