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	$57.28	8.153%	$61.95	$61.95	$61.95	$62.00
Purchase #2	$53.28	3.662%	$55.2311	$55.23	$55.25	$55.20
Purchase #3	$54.74	13.159%	$61.9432	$61.94	$61.95	$61.90
Purchase #4	$19.31	7.618%	$20.781	$20.78	$20.80	$20.80
Purchase #5	$165.97	11.672%	$185.342	$185.34	$185.35	$185.30
Purchase #6	$187.61	4.564%	$196.1725	$196.17	$196.15	$196.20
Purchase #7	$248.67	3.839%	$258.2164	$258.22	$258.20	$258.20
7 purchase totals =	$786.86		$839.6362	$839.63	$839.65	$839.60